Allergic rhinitis

Contents

Description

Alternative Names

Highlights

Introduction

Causes

Symptoms

Risk Factors

Prognosis

Diagnosis

Treatment

Other Treatments

Decongestants

Antihistamines

Corticosteroids

Immunotherapy

Prevention

Resources

References

Description

Alternative Names

Highlights

Drug Approval

Ciclesonide (Omanaris), a corticosteroid nasal spray, has been approved for treatment of seasonal and perennial allergic rhinitis (hay fever) in adults and children age 12 years and older.

FDA Drug Warnings

• The antihistamine promethazine (Phenergan) should not be given to children younger than age 2 because it may cause serious breathing problems.
• Omalizumab (Xolair) may cause a life-threatening allergic reaction (anaphylaxis). This drug is used to treat allergy-related asthma, but is also being investigated as an allergy treatment.

Cough and Cold Medicines for Children

In 2007, the FDA began reviewing the safety and effectiveness of cough and cold medicines for children. These medicines contain antihistamines, decongestants, expectorants, and cough suppressants. The FDA is particularly concerned about the use of these medicines in children younger than 2 years of age. Overdoses can cause serious heart problems and death. However, many experts are concerned that the currently recommended dosages are themselves not safe.

Immunotherapy (Allergy Shots)

• Immunotherapy is safe and effective for patients with allergic rhinitis, particularly those who have not been helped by other treatments, indicates a 2007 review in the Cochrane Database.
• An experimental DNA-based ragweed vaccine is showing promise in early clinical trials. In a 2006 pilot study published in the New England Journal of Medicine, six weekly injections of the vaccine helped improve symptoms with benefits lasting into the following ragweed season.

Allergic Rhinitis and Sleep

Allergic rhinitis can cause sleep disorders and interfere with sleep quality, indicates a 2006 study in the Archives of Internal Medicine. In the study of nearly 600 patients with allergic rhinitis, patients with severe allergic rhinitis experienced worse sleep problems than those with mild allergic rhinitis.

Allergic Rhinitis and Parkinson’s Disease

Allergic rhinitis may be associated with the later development of the neurological disorder Parkinson’s disease, suggests a 2006 study in Neurology. Both conditions are associated with an inflammatory response.

Introduction

The nose is separated into two passages by a wall of cartilage called the septum. The nasal passages are lined with a membrane that produces a clear liquid called mucus. Mucus is a one of the body's defense systems:

• The mucus traps small particles and bacteria, which may enter the nose as a person breathes.
• The trapped bacteria usually do not cause harm in healthy individuals.
• However, the bacteria can lead to a daily cycle of congestion and decongestion.
• When one side of the nose is congested, air passes through the open (decongested) side. The sides alternate between being wide-open and partly or completely blocked.

Rhinitis

If the congestion becomes severe or other changes occur that irritate the nasal passage, rhinitis develops. To be diagnosed with rhinitis, the patient must experience at least two of the following symptoms for an hour or more on most days:

• Runny nose
• Obstruction in the nasal passage
• Nasal itching
• Sneezing

Allergic rhinitis

These symptoms may occur as a result of colds or environmental irritants, such as allergens, cigarette smoke, chemicals, changes in temperature, stress, exercise, or other factors.

Infectious Rhinitis. If symptoms last less than 6 weeks, the condition is referred to as acute rhinitis and is usually caused by a cold or infection, or temporary overexposure to environmental chemicals or pollutants. [Infectious rhinitis is discussed in In-Depth Report #94: Colds and the flu.]

Chronic Rhinitis. When rhinitis lasts for a longer period, the condition is called chronic rhinitis. Allergies are often the cause, but structural problems or chronic infections could also be to blame.

Deviated septum

Adenoids

Causes

The allergic process, called atopy, and its connection to asthma is not completely understood. It involves various airborne allergens or other triggers that set off a cascade of events in the immune system leading to inflammation and hyperreactivity in the airways.

• The conductor in an orchestra of immune factors that contribute to allergies and asthma appears to be a category of white blood cells known as helper T cells, in particular a subgroup called Th2 cells.
• Th2 cells overproduce interleukins (ILs), immune factors that are molecular members of a family called cytokines, which are involved in the inflammatory process.

Antibodies

• Interleukins 4, 9, and 13 may be responsible for a first-phase asthma attack. These interleukins stimulate the production and release of antibody groups known as immunoglobulin E (IgE). People with both asthma and allergies appear to have a genetic predisposition for overproducing IgE.
• During an allergic attack, these IgE antibodies bind to special cells in the immune system called mast cells, which are generally concentrated in the lungs, skin, and mucous membranes. This bond triggers the release of a number of active chemicals, importantly potent molecules known as leukotrienes. These chemicals cause airway spasms, overproduce mucus, and activate nerve endings in the airway lining.
• Another cytokine, interleukin 5, appears to contribute to a late-phase inflammatory response. This interleukin attracts white blood cells known as eosinophils. These cells accumulate and remain in the airways after the first attack. They persist for weeks and mediate the release of other damaging particles that remain in the airways.

Better Hygiene, Fewer Childhood Infections

One theory blames the dramatic increase in asthma and allergies on the reductions in childhood infections that have occurred with modern hygiene and antibiotic use. The basic theory rests on the idea that infections stimulate production of specific immune factors called Th1 cells. As these cells build up, they replace other immune factors called Th2 cells, which react to allergens -- a less serious threat to the body. Without infections to stimulate the production of the Th1 infection fighters, the Th2 allergen fighters are not replaced, and they persist at high levels, making the growing child more susceptible to allergies and asthma.

A number of different studies support this theory:

• Some studies suggest that being part of a large family or attending day care increases the risk for early respiratory infections but reduces the risk of childhood asthma. The occasional cold, then, may be protective.
• In a 2002 study, researchers measured levels of bacterial byproducts called endotoxins in the mattress dust of 812 children. Those with the highest levels had an 80% lower rate in allergies and asthma.
• Another study further found a strong association between allergy development and the absence of certain beneficial bacteria (called probiotics) in infants' intestines. Infants who were born in more hygienic environments tended to lack these bacteria. Antibiotic overuse and modern hygiene may reduce these helpful organisms. (Probiotics are available in active yogurt cultures and in supplements, which are being studied for protection.)

According to many studies, the standard vaccinations against serious childhood infections pose no risk for developing asthma or hay fever. Some studies have even reported lower risk for asthma and allergies in the second and third years after vaccinations.

Overexposure to Indoor Allergens

Some evidence suggests that the increase in allergies and asthma may be due to overexposure to indoor allergens. These may include wall-to-wall carpeting, cats, and mold produced by dampness in homes. Children who spend hours indoor each day may become overexposed to indoor allergens. This exposure is intensified by the recent trend of making homes more energy-efficient, which may result in more dust mites being trapped inside. However, other studies suggest that early exposure to allergens may actually prevent the development of allergies in children.

Triggers of Seasonal Allergic Rhinitis (Hay Fever or Rose Fever)

Seasonal allergic rhinitis occurs only during periods of intense airborne pollen or spores. It is commonly, although inaccurately, called hay fever or rose fever, depending on whether it occurs in the late summer or spring. No fever accompanies this condition, and the allergic response is not dependent on either hay or roses. In general, triggers of seasonal allergy in the U.S. include:

• Ragweed. Ragweed is the most dominant cause of allergic rhinitis in the U.S., affecting about 75% of allergy sufferers. One plant can release 1 million pollen grains a day. Ragweed occurs everywhere in the U.S., although it is less common in western coastal states, southern Florida, northern Maine, Alaska, and Hawaii. The effects of ragweed in the northern states are first felt in middle to late August and last until the first frost. Ragweed allergies tend to be most severe before midday.
• Grasses. Grasses affect people in mid-May to late June. Grass allergies are experienced more in the late afternoon.
• Tree Pollen. Small pollen grains from certain trees usually produce symptoms in late March and early April.
• Mold Spores. Mold spores that grow on dead leaves and release spores into the air are common allergens throughout the spring, summer and fall. Mold spores may peak on dry windy afternoons or on damp or rainy days in the early morning.

Allergies

Major weather changes, such as El Nino, can affect the timing of allergy seasons. For example, in 1998, when the effects of El Nino were very strong, allergy attacks were markedly increased, and maximum tree pollen counts occurred 2 - 4 weeks earlier and mold counts 2 - 3 months earlier than the previous year.

Triggers of Perennial (Year-Round) Allergic Rhinitis

Allergens in the House. Allergens in the house can trigger attacks in people with year-long allergic rhinitis, called perennial rhinitis. Household allergens may include the following:

• House dust and mites. Dust mites, specifically mite feces, are coated with enzymes that contain a powerful allergen.
• Cockroaches
• Pet dander
• Molds growing on wallpaper, house plants, carpeting, and upholstery

However, some studies are suggest that early exposure to some of these allergens, including dust mites and pets, may prevent allergies from developing in the first place in children.

Fossil Fuels. There may be an association between traffic-related air pollution and allergic rhinitis. Some experts believe that refined fossil fuels, such as diesel fuel and particularly kerosene, are important triggers for allergic rhinitis. In people who already have allergies or asthma, exposure to such fossil fuels may worsen symptoms.

Symptoms

The general symptoms of rhinitis are congestion, runny nose, and postnasal drip, in which mucous drips into the throat from the back of the nasal passage, especially when lying on the back. Symptoms may vary depending on the cause of rhinitis. Symptoms of influenza and sinusitis must also be differentiated from allergies and colds.

Symptom Phases

Symptoms of allergic rhinitis occur in two phases, early and late.

Early Phase Symptoms. The early phase occurs within minutes of exposure to the allergens and includes:

• Runny nose
• Frequent or repetitive sneezing
• Itching in the nose, eyes, throat, or roof of the mouth

Late-Phase Symptoms. The late phase occurs 4 - 8 hours later and may include one or more of these symptoms:

• Nasal congestion and possibly plugged ears. Children may push their nose upward with the palm of their hand or twitch their nose rabbit-like to clear the obstruction.
• Fatigue.
• Mental changes can include irritability, a slight decrease in attention span, worsened memory, and slower thinking.
• Other common physical symptoms include a decreased sense of smell, plugged ears, sinus headache, postnasal drip or some combination. In severe allergies, dark circles may develop under the eye. The lower eyelid may be puffy and lined with creases.

Risk Factors

Allergic rhinitis affects between 20 - 40 million Americans of all ages. As with asthma and many upper respiratory infections, the incidence in allergic rhinitis is increasing. Allergies most often appear first in childhood, and allergic rhinitis is the most common chronic condition in childhood, although it can develop at any age. About 20% of allergic rhinitis cases are due to seasonal allergies, 40% to perennial (chronic) rhinitis, and the rest are mixed.

Family History

Genetic factors are the major determinants of allergies.

• If both parents have an allergy, the child's risk is 75%.
• If one parent is allergic, the child's risk is 50%.

Having Other Allergies

Having other allergies increases the risk for allergic rhinitis. Here are some examples:

• Young children who have eczema (an allergic skin reaction) have a later risk for allergic rhinitis and asthma. In fact, a family history of eczema increases the risk.
• Food allergies are associated with allergic rhinitis and asthma. (Early feeding patterns, time of weaning, and introduction of solid food do not appear to affect this risk.)
• Asthma, especially in patients who develop it as adults, may increase allergic sensitivity to ragweed and other allergens. Patients who have asthma and a genetic tendency towards allergies (atopy) are also at risk for rhinitis.

Other Factors Associated with Allergies

Birth Month. Some studies report a higher risk of allergies and asthma in children born in winter months and lower risk in those born during the summer.

Breastfeeding. Some researchers suggest that the dramatic increase in asthma and allergies may be due to fewer women breastfeeding their infants. In a number of studies, breastfeeding has been associated with a lower risk for allergies and asthma -- at least until age 2. Breastfeeding can also help prevent other upper respiratory infections. The American Academy of Pediatrics recommends feeding infants exclusively breast milk for the first 6 months of life.

Prognosis

Seasonal allergic rhinitis tends to diminish as a person ages. The earlier the symptoms start, the greater the chances for improvement. People who develop hay fever in early childhood tend not to have the allergy in adulthood. In one study, over half of allergic subjects reported that by 40 years of age their symptoms had decreased, and a quarter were symptom-free. In some cases, allergies go into remission for years and then return later in life. People who develop allergies after age 20, however, tend to continue to have hay fever at least into middle age.

People with allergic rhinitis may be at higher risk for other allergies, including potentially serious food or latex allergies.

Quality of Life

Although allergic rhinitis is not considered a serious condition, it nonetheless can interfere with many important aspects of life. A 2006 survey of nasal allergy sufferers reported that symptoms made patients feel tired (80%), miserable (65%), irritable (62%), and interfered with work performance (52%).

People with allergic rhinitis, particularly those with perennial allergic rhinitis, may experience sleep disorders and daytime fatigue. Often they attribute this to medication, but studies suggest congestion may be the culprit in these symptoms. In addition, a 2002 study indicated that patients with seasonal allergies experience hundreds of brief, subtle awakenings, called "microarousals," each night. In such cases, people are not aware that they wake up, but such events can cause fatigue the next day. A 2006 study of nearly 600 patients with allergic rhinitis found that sleep disorders and poor sleep quality were prevalent. Patients who had severe allergic rhinitis had worse sleep problems than those with mild allergic rhinitis.

Higher Risk for Asthma

Asthma and allergies often coexist, and the allergic response plays a strong role in childhood asthma. About 70 - 85% of children with asthma have allergies. Aggressive treatment of allergies in children with asthma can lower the risk for asthma attacks. Treating allergies in children may also help prevent the onset of asthma.

Chronic Swelling In the Nasal Passages (Turbinate Hypertrophy)

Any chronic rhinitis, whether allergic or nonallergic, can cause swelling in the turbinate, which may become persistent (turbinate hypertrophy). The turbinate is a tiny shelf-like bony structure that protrudes in the nasal passageways. It helps warm, humidify, and clean the air that passes over it. If turbinate hypertrophy develops, it causes persistent nasal congestion and, sometimes, pressure and headache in the middle of the face and forehead. This condition requires surgery.

Complications of Chronic Rhinitis in Children

• Children with severe allergies may have a higher risk for behavioral problems than those without allergies. Some research suggests that allergic rhinitis is responsible for 2 million missed school days each year.
• There have been reports that 30 - 45% of people with allergic rhinitis also suffer from ear infections (otitis media).
• Chronic nasal obstruction from year-round allergies can affect a child's appearance. If a child can only breathe through the mouth, the continual force of air passing through the oral cavity can change facial development. Such changes may include an elongated face and an overbite from teeth coming in at an abnormal angle.
• Chronic rhinitis can cause headaches and also affect a child's sleep, concentration, hearing, appetite, and growth.

Middle ear infection

Associations with Other Disorders

Depression. Some evidence has linked depression with allergies. A 2002 study, for example, found that people with depression reported a higher rate of allergic disorders (71%) compared to nondepressed individuals (43%). During allergy season, patients with allergies were more likely to experience mood changes, including sadness, lethargy, and mental fatigue, than at other times. Some evidence suggests that specific immune factors in the allergic response can cause depressive symptoms. Other research indicates that both may have a common cause.

Parkinson’s Disease. A 2006 study suggested that allergic rhinitis may be associated with the later development of the neurological disorder Parkinson’s disease. The researchers think that the inflammatory response may be the link between the two conditions. However, there is not yet any evidence that treating allergic rhinitis can prevent Parkinson’s disease.

Chronic Fatigue Syndrome (CFS). Some, although not all, studies have reported that a majority of patients with CFS also have allergies to foods, pollen, metals (such as nickel or mercury), or other substances. One theory is that allergens, like viral infections, may trigger a harmful overreaction of the immune system that can cause fatigue, joint aches, and fever as well as hormone and brain chemical disturbances. (However, most people with allergies do not have CFS.)

Diagnosis

To determine the cause of allergic rhinitis, the doctor will ask a number of questions about:

• Time of day and year of rhinitis episodes. Rhinitis that appears seasonally is typically due to pollens and outdoor allergens. If symptoms occur throughout the year, the doctor will suspect perennial allergic or non-allergic rhinitis.
• Family history of allergies.
• History of medical problems.
• In women, if they are pregnant or taking drugs that contain estrogen (oral contraceptives, hormone replacement therapy).
• Use of other medications including decongestants, which can cause a rebound effect.
• Pets.
• Any additional unusual symptoms. As examples, bloody nasal discharge and obstruction in only one nasal passage could suggest a tumor. Fatigue, sensitivity to cold, weight gain, and depression may be signs of hypothyroidism.

Physical Examination

The doctor will examine the inside of the nose with an instrument called a speculum. This is a painless examination allowing the doctor to check for redness and other signs of inflammation. The doctor will also usually check the eyes, ears, and chest.

Allergy Skin Tests

A skin test is a simple method for detecting common allergens. Patients are usually tested for a panel of common allergens. Skin tests are rarely needed to diagnose mild seasonal allergic rhinitis, since the cause is usually obvious. The skin test is not appropriate for children younger than age 3.

The procedure is as follows:

• Patients should not take antihistamines for at least 12 - 72 hours before the test. Otherwise an allergic reaction may not show up.
• Small amounts of suspected allergens are applied to the skin with a needle prick or scratch or are injected a few cells deep into the skin. The injection test may be more sensitive than the standard prick test.
• If an allergy is present, a hive (a swollen reddened area) forms within about 20 minutes.

The test is not completely accurate. For instance, a 2001 study reported that testing detected allergies in less than half of children with rhinitis. Furthermore, about 15 - 20% of people may have a skin reaction without actually having an allergy.

Laboratory Tests

Nasal Smear. The doctor may take a nasal smear. The nasal secretion is examined microscopically for factors that might indicate a cause, such as increased numbers of white blood cells, indicating infection, or high counts of eosinophils. High eosinophil counts indicate an allergic condition, but low counts do not rule out allergic rhinitis.

Tests for IgE. Blood tests for IgE immunoglobulin production may also be performed. One test is called the radioallergosorbent Test (RAST), used to detect increased levels of allergen-specific IgE in response to particular allergens. Blood tests for IgE may be less accurate than skin tests. They should be performed only on patients who cannot undergo skin testing or when skin test results are uncertain.

Imaging Tests

In people with chronic rhinitis, the doctor may also check for sinusitis. Imaging tests may be useful if other tests are ambiguous.

• A test called transillumination, in which a doctor shines a bright light against the patient's cheek or forehead, is an inexpensive method for checking for abnormalities in the sinus cavities, although it is not highly accurate.
• CT scans may be useful for some cases of sinusitis.

X-ray

Nasal Endoscopy

In certain cases of chronic or unresponsive seasonal rhinitis, a doctor may use endoscopy to examine for any irregularities in the nose structure. Endoscopy uses a tube inserted through the nose that contains a miniature camera to view the passageways.

Treatment

If rhinitis is caused by non-allergic conditions, particularly if there are accompanying symptoms indicating a serious problem, the doctor should treat any underlying disorders. If rhinitis is caused by medications, such as decongestants, the patient may need to stop taking them or find alternatives.

Preventing the Onset of Allergy Attacks

Patients with chronic allergic rhinitis may require daily medications. Patients with severe seasonal allergies should start medications a few weeks before the pollen season and continue taking them until the season is over. Effective medications include:

• Drugs that reduce the inflammatory response are important for preventing severe allergic rhinitis. Nasal corticosteroids (commonly called steroids) are now considered to be the most effective measure for preventing allergy attacks. Other anti-inflammatory drugs include leukotriene-antagonists and nasal cromolyn.
• Antihistamine tablets relieve sneezing and itching and can prevent nasal congestion before an allergy attack. Many brands are available by prescription and over-the-counter.
• Immunotherapy ("allergy shots") may be considered for patients with severe seasonal allergies that do not respond to treatment. It may also prevent asthma and the development of new allergies in children. Many experts now recommend immunotherapy for people with both asthma and allergies. Newer immunotherapeutic approaches using specially designed antibodies and vaccines are also showing promise.

All drug treatments have side effects, some very unpleasant and, in rare cases, serious. Patients may need to try different drugs until they find one that relieves symptoms without producing excessively distressing side effects.

Treating Nasal Symptoms of Allergic Rhinitis

Because seasonal allergies generally last only a few weeks, most doctors do not recommend the more potent prescription treatments for children. It is important for parents to determine if the child is actually under severe distress and that the parent is not simply responding to their own anxiety when they hear the child snorting or snoring. Prescription drugs are required only in severe cases. However, in children with both asthma and allergies, treatments for allergic rhinitis may also improve asthmatic symptoms.

Treating Mild Allergy Attacks. Mild allergy attacks usually require little more than reducing exposure to allergens and using a nasal wash. Dozens of treatments are available for allergic rhinitis. Many are available over-the-counter, but some require a prescription. They include the following:

• Nasal washes
• Decongestants that relieve nasal congestion and itchy eyes
• Decongestant/antihistamine combinations

Due to side effects, decongestants should not be used in children ages 14 years or younger. Also, overuse of nasal decongestions can actually worsen sinus congestion.

Treating Severe Allergic Rhinitis. Patients with chronic allergic rhinitis, particularly if they also have asthma, may require daily medications. These drugs include:

• Antihistamines. The newer non-sedating antihistamines -- such as cetirizine (Zyrtec), loratadine (Claritin), fexofenadine (Allegra), or desloratadine (Clarinex) -- cause less drowsiness than older antihistamines, such as Benadryl. Some of the newer drugs, such as Zyrtec and Clarinex, may also relieve nasal congestion.
• Anti-inflammatory drugs. Nasal corticosteroids are now considered to be the most effective measure for preventing allergy attacks. They are recommended for patients with very severe allergies that do not respond to antihistamines.
• Leukotriene-antagonists and nasal cromolyn may be beneficial in specific cases of allergies
• Immunotherapy ("allergy shots") works well for many patients with severe allergies. It is also proving to reduce asthma symptoms and the use of asthma medications in patients with known allergies.

Treating Itchy Eyes

Itching and redness in the eyes sometimes respond to oral antihistamines. Eye drops, however, provide faster relief, and a combination of the two may be best. The following are eye drops for itchy eyes. Others are also available. Individual responses vary, and patients need to find which specific treatment works best for them.

• Antihistamine eye drops: azelastine (Optivar), olopatadine (Patanol), ketotifen (Zaditor), levocabastine (Livostin) for relief of both nasal symptoms and itchy red eyes
• Decongestant eye drops: phenylephrine (Allergan Relief), naphazoline (Naphcon, Opcon-A, VasoClear), tetrahydrozoline (Murine Plus, Visine)
• Combination decongestant/antihistamine: Visine A.
• Corticosteroids: loteprednol (Lotemax, Alrex), pemirolast (Alamast).

General Side Effects and Warning.

• All eye drops can cause stinging, and some may result in headache and congestion.
• No one should continue taking eye drops if they experience pain, changes in vision, worsened redness, or irritation, or if the condition lasts more than 3 days.
• Do not touch the tip of the device to the eye or touch other surfaces with it. Replace the cap after using. Discard any solution that changes color or becomes cloudy.
• People who have heart disease, high blood pressure, an enlarged prostate gland, or glaucoma should talk to their doctor before taking these types of eye drops.

Other Treatments

For mild allergic rhinitis, a nasal wash can be helpful for removing mucus from the nose. You can purchase a saline solution at a drug store or make one at home (one cup of warm water, half teaspoon salt, pinch of baking soda). Over-the-counter saline nasal sprays that contain benzalkonium chloride as a preservative may actually worsen symptoms and infection.

Simple method for administering a nasal wash:

• Lean over the sink head down.
• Pour some solution into the palm of the hand and inhale it through the nose, one nostril at a time.
• Spit the remaining solution out.
• Gently blow the nose.

The solution may also be inserted into the nose using a large rubber ear syringe, available at a pharmacy. In this case the process is:

• Lean over the sink head down.
• Insert only the tip of the syringe into one nostril.
• Gently squeeze the bulb several times to wash the nasal passage.
• Then press the bulb firmly enough so that the solution passes into the mouth.
• Repeat the process in the other nostril.

Natural Remedies

Nearly half of asthma or allergy sufferers resort to alternative treatments. To date, however, little evidence supports treatments such as high-dose vitamins, homeopathic remedies, and most herbal remedies. Some relaxation methods, such as massage therapy, may be beneficial in reducing stress related to allergy symptoms. According to research presented at a 2004 allergy conference, acupuncture is now the most popular alternative treatment among allergy sufferers. The following are examples of recent areas of research:

• Acupuncture may provide symptom relief for persistent allergic rhinitis in children, according to results published in a 2004 pediatrics journal. The study compared the effects of active versus sham acupuncture. Larger trials are needed to confirm these results.
• Butterbur (also known as Petasites hybridus, butter dock, blatterdock, bog rhubarb, and exwort) is a plant found in Europe, North American, and parts of Asia. It is a traditional herbal remedy used for seasonal allergies and asthma. In a 2002 study, it was as effective and less sedating than a commonly prescribed antihistamine for treating seasonal allergies over a 2-week period.
• Probiotics are beneficial bacteria that may help protect against allergies and asthma. Probiotics are available in active yogurt cultures and in supplements, which are being studied for protection.

Decongestants

For mild allergic rhinitis, a nasal wash can be helpful for removing mucus from the nose. Decongestants may help dry nasal congestion. They work by shrinking vessels in the nose. By reducing blockage, they decrease the risk of developing sinusitis caused by viruses or bacteria. Many over-the-counter decongestants are available, either in tablet form or as nasal or inhaled decongestants that are applied directly into the airways as sprays, drops, or vapors.

Nasal-Delivery Decongestants

Nasal-delivery decongestants are applied directly into the nasal passages with a spray, gel, drops, or vapors. Nasal decongestants come in long-acting or short-acting forms. The effects of short-acting decongestants last about 4 hours; long-acting decongestants last 6 - 12 hours. The active ingredients in nasal decongestants include oxymetazoline, xylometazoline, and phenylephrine. Nasal forms work faster than oral decongestants and may not cause as much drowsiness. However, they can cause dependency and rebound.

Dependency and Rebound. The major hazard with nasal-delivery decongestants, particularly long-acting forms, is a cycle of dependency and rebound effects. The 12-hour brands pose a particular risk for this effect.

• With prolonged use (more than 3 - 5 days), nasal decongestants lose effectiveness and can cause swelling in the nasal passages.
• The patient then increases the frequency of the dose. As the congestion worsens, the patient may respond with even more frequent doses.
• This causes dependency and increased nasal congestion.

Tips for Use. The following precautions are important for people taking nasal decongestants:

• When using a nasal spray, spray each nostril once. Wait a minute to allow absorption into the mucosal tissues, and then spray again.
• Do not share droppers and inhalators with other people.
• Discard sprayers, inhalators, or other decongestant delivery devices when the medication is no longer needed. Over time, these devices can become reservoirs for bacteria.
• Discard the medicine if it becomes cloudy or unclear.

Oral Decongestants

Oral decongestants also come in many brands, which have similar ingredients. The most common active ingredient is pseudoephedrine (Sudafed, Actifed, Drixoral), sometimes in combination with an antihistamine. [The alternative decongestant, phenylpropanolamine (PPA) was taken off the market.] A small 2006 study reported that over-the-counter pseudoephedrine works just as well as the prescription drug montelukast (Singulair) in controlling allergic rhinitis symptoms. Patients in the study received a once-daily morning dose (240 mg) of ephedrine. Researchers suggest that taking pseudoephedrine in the morning, as opposed to later in the day or before bedtime, can help patients avoid side effects such as insomnia and nervousness.

Side Effects of Decongestants

Decongestants have certain adverse effects, which are more apt to occur in oral than nasal decongestants. These side effects include:

• Agitation and nervousness
• Drowsiness (particularly with oral decongestants and in combination with alcohol)
• Changes in heart rate and blood pressure
• Avoid combinations of oral decongestants with alcohol or certain drugs, including monoamine oxidase inhibitors (MAOI) and sedatives.

Individuals at Risk for Complications from Decongestants. People who may be at higher risk for complications are those with certain medical conditions, including disorders that make blood vessels highly susceptible to contraction. Such conditions include:

• Heart disease
• High blood pressure
• Thyroid disease
• Diabetes
• Prostate problems that cause urinary difficulties
• Migraines
• Raynaud's phenomenon
• High sensitivity to cold
• Emphysema or chronic bronchitis. (Individuals with these conditions should particularly avoid high-potency, short-acting nasal decongestant.)
• Medications that increase serotonin levels, such as certain antidepressants, anti-migraine drugs, diet pills, St. John's wort, and methamphetamine. The combination of these medicines and decongestants can cause blood vessels in the brain to narrow suddenly, causing severe headaches and even stroke.

Anyone with these conditions should not use oral or nasal decongestants without a doctor's guidance. Other people who should not use decongestants without first consulting a doctor include:

• Pregnant women
• Children. The American College of Chest Physicians advises against the use of over-the-counter decongestants and other cold medications in children ages 14 years or younger. Children are at particular risk for side effects that depress the central nervous system. Such symptoms cause changes in blood pressure, drowsiness, deep sleep, and, rarely, coma. In 2007, the FDA began reviewing the safety and effectiveness of cough and cold remedies for children.

Antihistamines

Histamine is one of the chemicals released when antibodies overreact to allergens. It is the cause of many symptoms of allergic rhinitis. Antihistamines can help relieve:

• Itching, sneezing, and nasal discharge
• Other allergy symptoms unrelated to rhinitis, including hives and some rashes
• Nasal congestion, for some of the newer antihistamines, such as cetirizine (Zyrtec) and desloratadine (Clarinex)

If possible, patients should take antihistamines before an anticipated allergy attack.

Many antihistamines are available. They include short-acting and long-acting forms and are available as tablets, nasal-inhalers, eye drops, and syrups. Antihistamines are generally categorized as first- and second-generation. First-generation antihistamines may cause more side effects than newer second-generation ones.

There are some notes of caution when taking any antihistamine:

• Antihistamines may thicken mucus secretions and can worsen bacterial rhinitis or sinusitis.
• Antihistamines can lose their effectiveness over time, and a different one may need to be tried.

First-Generation Antihistamines

First-Generation Antihistamines Ingredients and Brand Names. The older, so-called first generation antihistamines include:

• Diphenhydramine (Benadryl)
• Carbinoxamine (Clistin)
• Clemastine (Tavist)
• Chlorpheniramine (Chlor-Trimeton). Some health professionals recommend this drug if antihistamines are required during pregnancy. It may be as effective as the second generation antihistamines and much less expensive.
• Brompheniramine (Dimetane)
• Promethazine (Phenergan). This antihistamine should never be used for children younger than age 2 because it may cause life-threatening breathing problems.

First-generation antihistamines contain compounds called anticholinergics, which tend to produce more side effects than second-generation antihistamines.

Side Effects

• Drowsiness and impaired thinking
• Dry mouth
• Dizziness
• Agitation
• Insomnia or nightmares
• Sore throat
• Rapid heart beat and chest tightness (uncommon and should be reported)
• Men with enlarged prostate glands may experience difficulty urinating

Drowsiness and First-Generation Antihistamines. Drowsiness is the most distressing side effect reported from first-generation antihistamines, and is potentially serious. It may pose a higher than average risk for work-related and automobile accidents than alcohol, narcotics, or prescription sedatives. However, some studies have not found any strong differences in sedation between the first- and second-generation antihistamines. Still, experts caution against the first-generation antihistamines for people most at risk from sedative effects, particularly elderly individuals. To reduce risks, take the antihistamine at home a few hours before bedtime, and do not combine it with alcohol or tranquilizers. Do not drive or operate heavy machinery.

Second-Generation (Nonsedating) Antihistamines

The newer second-generation antihistamines do not contain anticholinergics, so they do not usually cause drowsiness to the extent that the first generation antihistamines do. They are sometimes referred to collectively as nonsedating antihistamines.

A major 2003 analysis reported that although Benadryl, the most common first-generation antihistamine, had a more negative effect on daily activities than the newer antihistamines, the differences were modest. Researchers in the study concluded that no clear distinction exists between the first- and second-generation antihistamines.

Brand Names. The second-generation drugs include:

• Loratadine (Claritin). Claritin is available over-the-counter and is approved for children ages 2 and older. Desloratadine (Clarinex) is similar to Claritin but stronger and longer-lasting. It is available only by prescription.
• Cetirizine (Zyrtec). Zyrtec is approved for both indoor and outdoor allergies. It is the only antihistamine to date approved for infants as young as 6 months. It is available over-the-counter.
• Fexofenadine (Allegra) is also available over-the-counter.
• Acrivastine (Semprex)
• Ebastine, norastemizole, levocetirizine, and mizolastine are other second-generation antihistamines under investigation in the U.S. and Europe. Some may prove to be useful for specific populations.

For nonprescription antihistamines, some studies suggest that cetirizine (Zyrtec) is more effective than Allegra or Claritin in improving symptoms, including those in children. However, cetirizine can cause drowsiness when taken at high doses.

Zyrtec and Claritin are approved for children younger than 5 years, although most antihistamines appear to be safe in children. Zyrtec is the only antihistamine approved for both indoor and outdoor allergies and for infants as young as 6 months. Both are available in syrup form. Studies with Zyrtec have reported fewer symptoms in children allergic to dust mites, and one study reported that infants with allergies who were given Zyrtec were much less likely to develop asthma later on than untreated infants. Claritin, at this time, is generally the preferred drug for young people, however, because it has the least negative effect on concentration and learning. Women who are pregnant or nursing should avoid these medications unless recommended by a doctor.

Side Effects and Precautions

• Common side effects include headache, dry mouth, and dry nose. (These are often only temporary and go away during treatment.)
• Drowsiness occurs in about 10% of adults and between 2 - 4% of children.
• Uncommon side effects include rapid heart beat and chest tightness. Tell your doctor if these effects occur.
• Extended-release forms of Claritin and Zyrtec have other ingredients that can cause other symptoms, including nervousness, restlessness, and insomnia. Some patients taking Claritin-D 24 Hour Extended Release tablets have reported obstruction in the upper gastrointestinal tract, including difficulty swallowing.

Drug and Food Interactions. Two earlier second generation drugs, terfenadine (Seldane) and astemizole (Hismanal), in rare cases, caused dangerous heart rhythm abnormalities, particularly in high doses or in people who had liver disease. They also caused interactions with certain other medications and grapefruit juice. Both Seldane and Hismanal have been taken off the market. Allegra, Zyrtec, and Claritin do not appear to pose any of the dangers associated with Seldane.

Until more is known, however, anyone who takes a second-generation antihistamine should probably avoid or use with caution combinations with grapefruit juice or the drugs that caused problems with Seldane and Hismanal. Such medications include:

• The antibiotics clarithromycin (Biaxin) and troleandomycin
• Certain HIV protease inhibitors
• Antidepressant serotonin-reuptake inhibitors (Prozac, Paxil, and Serzone)

Nasal-Spray Antihistamines

Azelastine (Astelin) and levocabastine (Livostin) are available in nasal spray form. They can reduce nasal congestion as well as allergy symptoms. Both reduce symptoms, although azelastine may be more effective in some patients. Their disadvantages are a bitter taste, drowsiness, and expense. They are not as effective as steroid nasal sprays.

Combination Antihistamines and Decongestants

Many prescription and non-prescription products that combine antihistamines and decongestants are available. Combinations sold over-the-counter include Allerest, Sudafed Severe Cold Formula, Vicks DayQuil, Benadryl Allergy/Sinus, Contac Day/Night Allergy & Sinus. Prescription combinations include Claritin-D, Allegra D, and Zyrtec-D. Symptoms may improve within 60 minutes, with congestion clearing up first.

Corticosteroids

A number of drugs are available for reducing the inflammatory response in allergies. These drugs can help prevent an allergy attack from occurring.

Corticosteroid Nasal Sprays

Nasal-spray corticosteroids (commonly called steroids) are considered the most effective drugs for treating severe allergic rhinitis. Corticosteroids suppress important stress and other hormones in a region of the brain called the HPA axis. The suppression of these hormones blocks the inflammatory response that triggers an allergic attack. Steroids do not relieve symptoms immediately. It may take several hours before their effects are felt. Nasal spray steroids benefits include:

• Reducing inflammation and mucus production
• Improving night sleep and daytime alertness in patients with perennial allergic rhinitis
• Treating polyps in the nasal passages

Comparison studies report that nasal steroid sprays work better than second generation antihistamines, such as loratadine (Claritin) and cetirizine (Zyrtec), and are possibly even more effective than allergy shots. They have no effect on itchy eyes, however.

Nasal-Spray Brands. Corticosteroids available in nasal spray form include:

• Triamcinolone (Nasacort). Approved for children over age 6.
• Mometasone furoate (Nasonex). Approved for use in patients age 3 and older.
• Fluticasone (Flonase, Flounce, generic). Approved for children over age 4.
• Beclomethasone (Beconase, Vancenase), flunisolide (Nasalide), and budesonide (Rhinocort). Approved for children over age 6.
• Ciclesonide (Omnaris). Approved for patients age 12 and older.

Side Effects. Corticosteroids are powerful anti-inflammatory drugs. Although oral steroids can have many side effects, the nasal-spray form affects only local areas and has less risk for widespread side effects unless the drug is used excessively. Side effects of nasal steroids may include:

• Dryness, burning, stinging in the nasal passage
• Sneezing
• Headaches and nosebleed (uncommon but should be reported to your doctor immediately)

Possible Long-Term Complications. All corticosteroids suppress stress hormones. This effect is known to produce some serious long-term complications in people who take oral steroids. Researchers have found far fewer concerns with nasal administration or inhaled forms, but there may be certain problems:

• Effect on growth. The major concern for children is whether nasal steroids, like other forms of steroids, will adversely affect growth. Studies report either a temporary and slight (about half an inch) early effect on growth or no effect at all.
• Effect on eyes. Glaucoma is a known side effect of oral steroids. Some ophthalmologists have observed higher pressure in the eye (a sign of glaucoma) in some patients taking nasal steroid sprays. (Studies have found no increased risk for cataracts in young people who have taken intranasal steroids). The eye pressure appears to return to normal after stopping the steroid, but periodic eye examinations are advised.
• Use during pregnancy. Steroids appear to be safe during pregnancy, but pregnant women should talk to their doctor about other options before taking them.
• Nasal passage injury. Steroid sprays may injure the nasal septum (the bony area that separates the nasal passage) if the spray is directed onto it. This complication is very rare.
• Lower resistance to infection. People with any infectious disease or injury in the nose should not take these drugs until the disease or wound has been treated and cured.

Cromolyn

Cromolyn serves as both an anti-inflammatory drug and a specific blocker for allergens. The standard cromolyn nasal spray (Nasalcrom) is not as effective as steroid nasal sprays but does work well for many people with mild allergies. It is one of the preferred first-line therapies for pregnant women with mild allergic rhinitis. It may take up to 3 weeks to experience full benefit.

Side Effects. Cromolyn has no major side effects, but minor ones include nasal congestion, coughing, sneezing, wheezing, nausea, nosebleeds, and dry throat. The spray can cause burning or irritation.

Leukotriene-Antagonists

Leukotriene-antagonists are oral drugs that block leukotrienes, powerful immune system factors that are important in causing airway constriction and mucus production in allergy-related asthma. Leukotriene-antagonists include zafirlukast (Accolate), montelukast (Singulair), zileuton (Ziflo), and pranlukast (Ultair, Onon). These drugs are mainly used to treat asthma. Montelukast was approved in 2003 to treat seasonal allergies, and in 2005 to treat indoor allergies.

Immunotherapy

Immunotherapy (commonly referred to as "allergy shots") is a safe and effective treatment for patients with allergies. It is based on the premise that people who receive injections of a specific allergen will lose sensitivity to that allergen. The most common allergens for which shots are given are house dust, cat dander, grass pollen, and mold.

Immunotherapy benefits include:

• Targeting the specific allergen.
• Reducing sensitivity in airways in the lungs as well as in the upper airways.
• Preventing the development of new allergies in children.
• Reducing asthma symptoms and the use of asthma medications in patients with known allergies. Research suggests it may also help prevent the development of asthma in children with allergies.

Candidates

Candidates for Immunotherapy. Immunotherapy may be given to anyone over age 7 whose allergies are severe and who do not respond to medication. Many experts agree that immunotherapy should be considered as soon as possible for children with asthma and allergies. Immunotherapy is safe for pregnant women who are already receiving it, although half-strength doses are generally recommended, and it should not be started during pregnancy.

Individuals at Risk for Complications. People who should probably avoid immunotherapy include those who have:

• An extreme response to skin tests (this may predict an allergic reaction).
• Wheezing.
• Uncontrolled severe asthma or lung disease.
• Patients taking certain medications (such as beta-blockers).
• The health status of anyone should be determined before starting treatment.

Administering Therapy

The major downside to immunotherapy is that it requires a prolonged course of weekly injections. The process generally includes:

• Injections of diluted extracts of the allergen are given on a regular schedule, usually twice a week to weekly at first, then in increasing doses until a maintenance dose has been reached. It usually takes several months and may take up to 3 years to reach a maintenance dose.
• At that time, intervals between shots can be 2 - 4 weeks, and the treatment is continued for another 3 - 5 years.
• Patients can experience some relief within 3 - 6 months. If there is no benefit within 12 - 18 months, discontinue the shots.

After stopping immunotherapy, about a third of allergy sufferers no longer have any symptoms, a third have improved symptoms, and a third relapse.

The use of an injection series is effective, but patients often fail to comply with the regimens. Some other schedules and delivery methods are being investigated that might make the program easier and less distressing.

Rush Immunotherapy. Investigators are studying "rush immunotherapy," in which patients achieve the full maintenance dose with several shots a day over a period of 3 - 5 days. Rush therapy uses modifications that reduce the risk of severe reactions to excessive doses. Studies suggest that it is effective and safe, with few side effects other than itching. Patients must be monitored closely during this period, however, for severe reactions.

Oral Forms. Trials are underway to test oral forms of immunotherapy as an alternative to allergy shots. These methods include using a pill taken by mouth or a sublingual (under-the-tongue) tablet. Although oral and sublingual immunotherapy is prescribed in many countries in Europe and South America, it is not approved in the United States and is not considered accepted therapy at this time.

Side Effects and Complications of Immunotherapy

Injections for ragweed and, sometimes, dust mites have higher risks for side effects than other allergy shots. If complications or allergic reactions develop, they usually occur within 20 minutes, although some can develop up to 2 hours after the shot is given.

Side effects of immunotherapy include:

• General itching, swelling, red eyes, hives, soreness at the injection site.
• Less common side effects are low blood pressure, asthma worsening, or difficulty breathing. This is due to an extreme hypersensitivity response called anaphylaxis. It can also occur if excessive doses are given.
• In rare cases, particularly because of excessive doses or if a patient has a serious lung problem, severe reactions can occur, which can be life threatening.
• Premedicating patients with antihistamines and corticosteroids may help reduce the risk of reactions to immunotherapy, although this could mask early warning signs.

In a 10-year study, the incidence of any adverse effect was less than two-tenths of 1%, and the great majority of events were mild. The risk for a fatal response is estimated to be 1 in 63 million injections. (As a comparison, the risk for a fatal reaction to penicillin is much higher, 1 in 7.5 million injections.)

Investigational Immunotherapy Approaches

Vaccines. Of particular interest is the development of immunotherapeutic vaccines that use more specific targets to produce an insensitivity to allergens. One such vaccine uses a small protein from the allergen, which is injected into the patient. Other vaccines under investigation are those that use the allergen's genetic material (its DNA) to promote tolerance to the allergen. In a promising 2006 pilot study, patients who received 6 weekly injections of a DNA-based experimental ragweed vaccine had symptom reductions that lasted a year later into a second ragweed season. Researchers will be testing this vaccine in further clinical trials.

Monoclonal Antibodies. Monoclonal antibodies (MAb) are genetically-developed antibodies that are designed to target and attack very specific factors. A MAb known as omalizumab (Xolair) prevents the antibody immunoglobulin E (IgE) from triggering the inflammatory events that lead to allergies. Studies in recent years have suggested that omalizumab may help reduce symptoms and improve quality of life for patients with non-seasonal allergic rhinitis. A 2006 study suggested that treatment with omalizumab before and during ragweed allergy shots may help reduce immunotherapy side effects. The drug is currently approved for asthma. In 2007, the FDA warned that omalizumab may cause a life-threatening allergic reaction (anaphylaxis) in some patients.

Prevention

People with existing allergies should avoid irritants or allergens. These triggers include:

• Pollen. This is the primary cause of allergic rhinitis.
• Dust mites, specifically mite feces, which are coated with enzymes that contain a powerful allergen. These are the primary allergens inside the home.
• Animal dander (flakes of skin) and hair from cats, house mice, and dogs. House mice are proving to be significant sources of allergens, particularly in urban children.
• Molds.
• Fungi.
• Cockroaches are major asthma triggers and may reduce lung function even in people without a history of asthma.
• Some research suggests that alcohol intake may influence allergy severity. One study found that as little as one drink a day is enough to worsen dust mite allergies.
• Some studies suggest that early exposure to some of these allergens, including dust mites and pets, may actually prevent allergies from developing in children.

Indoor Protection Against Allergens

Controlling Pets. People who already have pets and are not allergic to them are probably at low risk for developing such allergies later on. When children are exposed to more than one dog or cat during their first year, they have a much lower risk for not only pet allergies but also seasonal allergies and asthma. (Pet exposure does not protect them from other allergens, notably dust mites and cockroaches).

In children who have an existing allergy to pets, however, the pets should be given away or kept outside. If this isn't possible, they should at least be confined to carpet-free areas outside the bedroom. Cats harbor significant allergens, which can even be carried on clothing. Dogs usually present fewer problems. Washing animals once a week can reduce allergens. Dry shampoos, such as Allerpet, that remove allergens from skin and fur and are now available for both cats and dogs and are easier to use than wet shampoos.

For small children, stuffed animals might serve as a comforting replacement, although they might harbor dust mites. Putting stuffed animals in the freezer for 24 hours before washing them kills the dust mites. For best effect, this process should be done weekly.

Preventing Exposure to Cigarette and Cooking Smoke. Parents who smoke should quit. Studies show that exposure to second-hand smoke in the home increases the risk for asthma and asthma-related emergency room visits in children. [For help in quitting, see In-Depth Report # 41: Smoking.]

Controlling Dust. Spray furniture polish is very effective for reducing both dust and allergens. Air cleaners, filters for air conditioners, and vacuum cleaners with High Efficiency Particulate Air (HEPA) filters can help remove particles and small allergens found indoors. Neither vacuuming nor the use of anti-mite carpet shampoo, however, is effective in removing mites in house dust. Vacuuming actually stirs up both mites and cat allergens. People with these types of allergies should avoid having carpets or rugs in their homes.

Bedding and Curtains. Many experts recommend reducing exposure to dust mites by enclosing mattresses and pillows in semipermeable coverings. (Vinyl mattress covers limit airflow and may worsen, or even cause, asthma in children.) However, several 2005 studies suggested that such covers do not prevent allergies or asthma. Curtains should be replaced with shades or blinds and bedding washed using the highest water temperature setting.

Reducing Humidity in the House. Dust mites thrive in humidity, and damp houses increase the risk for mold. On-going humidifiers can worsen the problem. If they are used, humidity levels should not exceed 40%, and humidifiers should be cleaned daily with a vinegar solution.

Exterminating Pests (Cockroaches and Mice). Use professional exterminators to eliminate cockroaches. (One study reported that ridding a home of cockroaches and cleaning the house using standard housecleaning techniques failed to eliminate the cockroach allergens themselves.) Exterminate mice and attempt to remove all dust, which might contain mouse urine and dander.

Outdoor Protection

Avoiding Outdoor Allergens. The following are some recommendations for avoiding allergens outside:

• Start taking allergy medications 1 - 2 weeks before ragweed season begins. Be sure to take allergy medications before going outside. If regular medications do not work, ask your doctor about allergy shots.
• Camping and hiking trips should not be scheduled during times of high pollen count (May and June for grass pollen and September to October for ragweed).
• Patients who are allergic should avoid barns, hay, raking leaves, and mowing grass. (A mask can be worn during outdoor chores to help reduce pollen exposure.)
• Sunglasses can help prevent pollen from getting into eyes.
• After being outdoors, clean off pollen residue by bathing, washing hair and clothes, and using a nasal salt water rinse.

Dietary Factors

Some evidence suggests that people with allergic rhinitis and asthma may benefit from a diet rich in omega-3 fatty acids (found in fish, almonds, walnuts, pumpkin, and flax seeds) and fruits and vegetables (at least five servings a day). Some studies also suggest reducing sodium, trans fatty acids (hydrogenated fats found in commercial products and baked goods), and omega-6 fatty acids (found in most vegetable oils). Investigators are also studying probiotics -- so-called good bacteria, such as lactobacillus and bifidobacterium, which can be obtained in supplements.

Resources

• www.aaaai.org -- American Academy of Allergy, Asthma & Immunology
• www.acaai.org -- American College of Allergy, Asthma & Immunology
• www.niaid.nih.gov -- National Institute of Allergy and Infectious Diseases
• www.njc.org -- National Jewish Medical and Research Center
• www.lungusa.org -- The American Lung Association

References

Bower JH, Maraganore DM, Peterson BJ, Ahlskog JE, Rocca WA. Immunologic diseases, anti-inflammatory drugs, and Parkinson disease: a case-control study. Neurology. 2006 Aug 8;67(3):494-6.

Calderon M, Alves B, Jacobson M, Hurwitz B, Sheikh A, Durham S. Allergen injection immunotherapy for seasonal allergic rhinitis. Cochrane Database Syst Rev. 2007 Jan 24;(1):CD001936.

Creticos PS, Schroeder JT, Hamilton RG, Balcer-Whaley SL, Khattignavong AP, Lindblad R, et al. Immunotherapy with a ragweed-toll-like receptor 9 agonist vaccine for allergic rhinitis. N Engl J Med. 2006 Oct 5;355(14):1445-55.

Leger D, Annesi-Maesano I, Carat F, Rugina M, Chanal I, Pribil C, et al. Allergic rhinitis and its consequences on quality of sleep: An unexplored area. Arch Intern Med. 2006 Sep 18;166(16):1744-8.