Allergies overview

Allergy symptoms include itchy eyes and skin, sneezing, nasal congestion, wheezing, and rash. Seasonal allergies result from grass, weed, tree pollen, or molds. Cat and dog dander allergies are common. Food allergies include peanut or milk.

An allergy is an inappropriate immune system response (causing symptoms) to substances that, in most people, cause no response. The response is mainly to harmless substances that come in contact with the respiratory airways, skin, or eye surface. Common allergens are pollen, spores, housedust mites, and animal dander. Certain drugs, and some foods, most commonly dairy products, seafood, strawberries, and cereals, can also cause allergies. In diagnosing an allergy, the individual’s medical history is important. The doctor needs to know if the symptoms vary according to the time of the day or the season, and if there are pets or other likely sources of allergens in the home.

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Allergies in detail - non-technical

Allergies are hypersensitive responses by the immune system to otherwise harmless foreign substances.

Demographics

Allergies are among the most common medical disorders. It is estimated that 60 million Americans, or more than one in every five, suffer from some form of allergy that is pronounced enough to cause symptoms. More than half of all Americans test positive for one or more allergens. Allergies are the third leading cause of chronic disease among American children and the single largest reason for school absences. Allergies are the fifth leading cause of chronic disease among all Americans, accounting for one in nine physician visits and a major source of lost workplace productivity. There are similar proportions of allergy sufferers throughout much of the world.

Among Americans:

• Approximately 36 million suffer from seasonal allergies, with seasonal allergic rhinitis—or hay fever— affecting 20% of all adults and up to 40% of children. Pollen allergies generally develop between the ages of 6 and 13. Other respiratory allergies, such as those to dust, animal dander, and molds, may occur in children as young as two or three.
• Approximately 12 million have food allergies, including 4% of adults and 6-8% of children four years-of-age and under. Approximately 6.9 million Americans are allergic to seafood and 0.4-0.6% are allergic to peanuts and other nuts—the most severe of food allergies.
• Allergic drug reactions account for 5-10% of all adverse drug reactions, with skin reactions being the most common. About one-fifth of all children are allergic to some type of medication, often penicillin, sulfa drugs, or aspirin.
• Although about 15% of adults have mild, localized allergic reactions to insect bites and stings, approximately 3% have serious allergies to the venom of stinging insects, such as honeybees, wasps, hornets, yellow jackets, and fire ants (which are found only in the South). Children rarely experience the severe reactions to venom that sometimes occur in adults.
• Hives affect up to 20% of the population at some point in their lives.
• Skin allergies or allergic contact dermatitis is the most common skin condition in children under age 11.
• Estimates of the prevalence of latex allergy vary from less than 1% to 6%. Healthcare workers are particularly at risk for contact dermatitis from latex gloves.

Almost nine million American children suffer from asthma, a chronic disease that causes inflammation of the airways, making it difficult to breathe. Many different allergens can trigger asthma attacks and it is estimated that 50% of adults and more than 80% of children with asthma have associated allergies, especially allergic rhinitis. It is believed that asthma is both under-diagnosed and under-treated in the elderly.

Anaphylaxis or anaphylactic shock is a rare, severe, and potentially fatal allergic reaction that causes blood pressure to drop severely and the airways to swell shut.

Among Americans:

• More than 700 die each year from anaphylaxis brought on by an allergic reaction
• Approximately 150–200 die from food-induced anaphylaxis
• Penicillin in its various forms results in about 400 deaths per year in the United States. Worldwide, 32 out of every 100,000 patients exposed to penicillin have an anaphylactic reaction
• Each year 40–100 Americans die from an anaphylactic reaction to insect bites or stings
• There are about 220 cases of anaphylaxis and three deaths annually from latex allergy

The incidence of allergies and asthma is increasing in industrialized countries by about 5% per year and as many as half of all those affected are children. Some of this increase can be attributed to better diagnosis and reporting. However much of it may be due to lifestyle and environmental factors.

Description

An allergy is a type of immune response. The immune system normally responds to microorganisms, such as bacteria or viruses, or foreign particles by producing specific proteins called antibodies. These antibodies identify and bind to a specific foreign molecule—known as the antigen. The reaction between the antibody and its antigen sets off a series of chemical reactions designed to protect the body from infection. However with allergies, this immune response is triggered by harmless common substances called allergens. Allergens may be inhaled into the lungs (pollen, dust, animal dander, mold, pollutants), swallowed (food, drugs), injected (drugs, insect venom), or touched (poisonous plants, latex).

There are two main types of allergic reactions. Immediate hypersensitivity reactions are mediated predominately by a type of immune-system cell called a mast cell and occur within minutes of contact with the allergen. Delayed hypersensitivity reactions are mediated by T cells, a type of white blood cell, and occur hours to days after exposure to the allergen.

In immediate sensitivity reactions allergens bind to a type of antibody called immunoglobulin E or IgE on the surface of mast cells. Mast cells are filled with granules that contain a variety of potent chemicals including histamine. When the IgE on a mast cell binds its specific allergen, the contents of the granules spill out onto neighboring cells. Histamine binds to proteins called histamine receptors on the surfaces of these other cells, causing a chain of reactions that lead to allergy symptoms. Histamine binding to receptors on blood vessels increases leakage, leading to the fluid accumulation, swelling, and redness. In the nasal passages histamine causes swelling, congestion, and increased mucus production. Histamine also stimulates pain receptors on nerve cells, causing sensitivity and irritation. These symptoms last from one to several hours following contact with the allergen.

In delayed hypersensitivity reactions roving T cells contact the allergen, setting in motion a more prolonged immune response. This type of allergic response may develop over several days following contact with the allergen and symptoms may persist for a week or more.

Allergens enter the body through four main routes: the airways, the gastrointestinal tract, the circulatory system, and the skin. Inhaled or ingested allergens usually cause immediate hypersensitivity reactions. Allergens on the skin usually cause delayed hypersensitivity reactions.

People are sensitive to different allergens. For example, some people have severe allergic rhinitis but no food allergies, whereas others are extremely sensitive to nuts but not to any other food. Allergies may worsen over time. For example, allergic rhinitis can be either seasonal or chronic and a childhood ragweed allergy may progress to year-round dust and pollen allergies. Conversely, people can lose allergies. Infant or childhood atopic dermatitis, for example, almost always disappears with advancing age. However most often, an apparent loss of sensitivity is due to reduced exposure to the allergen or increased tolerance for the allergy symptoms.

Risk factors

Although allergies to specific allergens are not inherited, the propensity for developing allergies is frequently inherited.

• If neither parent has allergies, the chances of a child developing allergies are approximately 10–20%.
• A child with one allergic parent has a 30–50% chance of developing allergies.
• The likelihood of developing allergies rises to 40–75% if both parents have allergies. However children are not necessarily sensitive to the same allergens as their parents. Since people with allergies tend to produce more IgE than those without allergies, it may be that the tendency to produce more IgE is inherited. High levels of IgE also increase the likelihood of having allergies to multiple allergens.

Other risk factors for the development of childhood allergies include:

• low birth weight
• being born during a high-pollen season
• not being breastfed
• growing up in a home with tobacco smoke
• having a family pet
• having a lower socioeconomic status
• repeated exposure to an allergen or prolonged exposure to a strong allergen

Causes and symptoms

The most common airborne allergens are:

• plant pollens
• animal fur and dander
• body parts from house mites (microscopic creatures found in all houses)
• house dust
• mold spores
• feathers
• cigarette smoke
• chemicals
• solvents
• cleansers

Pollen can cause both seasonal and chronic rhinitis. Seasonal rhinitis occurs at the same time every year and is caused by the pollen of specific plants, especially grasses and trees in the spring and ragweed in the late summer and fall. Allergies tend to worsen as the season progresses because the immune system becomes sensitized to particular antigens and produces a faster, stronger response. Chronic rhinitis can be caused by food as well as airborne allergens. Airborne allergens cause immediate hypersensitivity reactions in the upper airways and eyes. These include sneezing, runny nose, itchy, watery, and bloodshot eyes, nasal congestion, and scratchy or irritated throat due to postnasal drip.

Airborne allergens can also cause inflammation of the thin membrane (conjunctiva) covering the eye, resulting in the redness, irritation, and increased tearing of allergic conjunctivitis or pink eye. Asthma causes wheezing, coughing, and shortness of breath and is associated with exposure to numerous allergens including cockroach allergens.

Common food allergens include:

• cow’s milk
• eggs
• grains such as wheat or corn
• nuts, especially peanuts, walnuts, and Brazil nuts
• fish, mollusks, and shellfish
• soy products
• some fruits, especially raw seeded fruit
• some vegetables, especially tomatoes or legumes such as peas or beans
• chocolate
• certain spices
• food additives and preservatives

True food allergies are often confused with intolerance to certain foods. Food allergies, like other types of allergies, are caused by an antibody response, whereas intolerance is due a deficiency in the enzymes needed to digest a certain food. For example, a milk allergy is caused by sensitivity to an allergen (often the protein lactalbumin) in the milk itself. In contrast, people who lack the enzyme lactase have lactose intolerance—the inability to digest one of the sugars in milk—and suffer from gastrointestinal problems when they consume milk or certain milk products.

Symptoms of food allergies depend on the tissues that are most sensitive to the allergen and whether the allergen has spread systemically through the circulatory system. Allergens in food can cause immediate hypersensitivity reactions that include itching, swelling, and/or rashes of the eyes, lips, mouth, and throat. Food allergies can also cause respiratory symptoms. Swelling and irritation of the intestinal lining can cause nausea, vomiting, cramping, diarrhea, and gas. When food allergens enter the bloodstream from the gastrointestinal tract, they can cause hives, atopic dermatitis, or more severe reactions such as angioedema. Some food allergens may cause anaphylaxis, a potentially life-threatening condition marked by tissue swelling, airway constriction, and drop in blood pressure. Reactions to peanuts and other nuts can be so dangerous that physicians recommend caution in giving these foods to infants and children with a family history of allergy. Some school systems are restricting the use of peanuts and peanut butter in lunchrooms or banning them altogether, since even smelling or touching them can cause an allergic reaction in some children.

Drugs that often cause allergic reactions include:

• penicillin and other antibiotics
• flu vaccines
• tetanus toxoid vaccine
• gamma globulin

Insects and other arthropods whose bites or stings may cause an allergic reaction include:

• bees, wasps, and hornets
• mosquitoes fleas
• scabies

Injected allergens from drugs or insect bites and stings are introduced directly into the circulation where they can cause both local reactions, such as swelling and irritation at the injection site, and system- wide (systemic) reactions, including anaphylaxis. Symptoms of an allergy to insect venom include:

• hives
• itchy eyes
• a dry cough
• constriction of the throat and chest
• nausea
• dizziness
• abdominal pain

There are three main types of allergic skin reactions:

• atopic dermatitis or eczema
• hives (urticaria)
• contact dermatitis

Atopic dermatitis and eczema are skin reactions to allergens introduced through the airways or gastrointestinal tract. Eczema commonly occurs in infants and children with a family history of allergies and is usually outgrown by the age of six. It generally occurs in cycles, beginning with dry, itchy skin that becomes inflamed when scratched, followed by weeping sores that subsequently crust over. In the chronic stage the affected skin becomes thickened, leathery, and scaly. Eczema appears most often on the cheeks, ears, and neck and the inner folds of elbows and knees, but it may affect other parts of the body as well.

Whole-body or systemic reactions can occur with any type of allergen, but are more common following ingestion or injection of an allergen. Hives are a systemic skin reaction characterized by raised, red, itchy blotches of varying sizes anywhere on the body, but especially on the stomach, chest, arms, hands, and face. Angioedema is a deeper, more extensive, and painful reaction in which fluid accumulation causes recurrent, non-inflammatory swelling of the skin, eyelids, lips, mucous membranes, genitals, other organs, and brain. However it most often occurs on the extremities, fingers, toes, and parts of the head, neck, and face. Hives and angioedema are usually acute conditions, although they can sometimes persist for weeks.

Skin contact with allergens can cause reddening, itching, and blistering, known as contact dermatitis. The dermatitis sometimes has an identifying pattern, such as the outline of an earring or latex glove. Common causes include:

• poison ivy, oak, and sumac
• nickel or nickel alloys
• chemicals
• cosmetics
• latex

Dermatitis can also be caused by non-allergic damage to skin cells arising from irritants such as cold, soap, or chemical agents.

Asthma is a chronic, reversible respiratory disorder caused by obstruction and swelling of the airways to the lungs. An asthma attack begins when the muscles surrounding the bronchial tubes spasm and the tubes narrow. This stimulates increased mucus production, further blocking the airways, and inflammation and swelling, which cause even more congestion and discomfort. Symptoms of asthma include coughing, wheezing, shortness of breath, fatigue, anxiety, and tightness in the chest. Asthma can be triggered by allergens—including pollen, animal dander, dust, and certain foods—and by non-allergenic irritants.

Anaphylaxis is an IgE-mediated hypersensitivity reaction brought about by mediators released by mast cells in the tissues and by immune system cells called basophils in the blood. These can cause airway constriction, blood pressure drop, widespread tissue swelling, heart rhythm abnormalities, and sometimes loss of consciousness. Other symptoms may include dizziness, weakness, seizures, coughing, flushing, or cramping. Symptoms can begin within five minutes after exposure to the allergen or up to an hour or more later. Anaphylaxis is most often associated with allergies to foods, medications, and insect venoms.

Genetic profile

The genetic predisposition toward the development of hypersensitivity reactions upon exposure to specific antigens is called atopy. After birth the immune system switches to become either non-allergy prone (TH1) or allergy prone (TH2), depending on an interplay of heredity and environment. TH stands for T-helper white blood cells. TH1 cells fight bacteria and viruses and protect against allergies. TH2 cells fight parasitic infections and promote the production of excessive IgE, increasing the likelihood of developing allergies. TH2 immunity is much more likely to be switched on in children with a family history of allergies.

Over the past four decades atopy has increased significantly, for reasons that are not well understood. In addition to genetic factors, it has been suggested that our environment contains more allergy-inducing substances and that protective factors may have been removed from the environment. There is also some evidence suggesting that the worldwide fight against infectious disease and increased personal cleanliness may be interfering with immune system function. Global warming—and the accompanying changes in natural vegetation patterns and increased pollen production—may also be affecting atopy.

Diagnosis

Examination

Allergies can often be diagnosed by a careful medical history that matches the onset of symptoms with exposure to possible allergens. Allergy is suspected if the symptoms are characteristic of an allergic reaction and occur repeatedly upon exposure to the suspected allergen, at a certain time of year, or in a particular environment. Although allergy tests can be used to identify potential allergens, their results must be supported by evidence of an allergic response.

Tests

With allergy skin tests a tiny dose of an aqueous extract of the suspected allergen is pricked, scratched, punctured, or patched on the skin. The initial test is usually a prick or patch test on the back, forearm, or top of the thigh. Reactions are usually evaluated about 15 minutes after exposure. An allergen may produce a classic immune wheal-and-flare response—a skin lesion with a raised, white, compressible area surrounded by a red flare. A positive skin reaction will occur even if the allergen is normally encountered in the airways or in food. Skin testing can produce false positives and, occasionally, serious allergic reactions. Intradermal skin tests involve injection of the allergen into the dermis of the skin. These are more sensitive and use smaller amounts of allergen, so they can be used with potentially fatal allergens such as antibiotics.

Provocation tests administer the allergen directly through its normal route under medically controlled conditions. Food allergen provocation tests involve the ingestion of a measured amount of the suspected allergen in an opaque capsule after abstinence from the suspected allergen for two weeks or more. The results are compared to the response to ingestion of a placebo. Diagnosis of delayed allergic contact dermatitis involves the application of a skin patch containing the allergen. Provocation tests are never used when a patient’s medical history suggests the possibility of anaphylaxis.

Since people with allergies may have a higher level of total IgE in their serum(the portion of the blood that contains antibodies) than those without allergies, total IgE can be measured with a two-site immunometric assay. However there is considerable overlap in serum IgE levels among people with and without allergies. Furthermore other non-allergic conditions—including smoking, HIV/AIDS, parasitic infections, and IgE myeloma—can raise IgE levels. However a total serumIgE test is useful for diagnosing some conditions.

With allergen-specific IgE measurements, the suspected allergen is bound to a solid support, such as a cellulose sponge, microtiter plate, or paper disk. A patient’s serum is incubated with the allergen. Allergen-specific IgE antibodies will bind to the solid phase and remain there when the serum is washed off. A second labeled antibody that binds to any IgE is added to determine the level of the allergen-specific IgE. The radioallergosorbent test (RAST) uses radioactive anti-IgE antibodies. A newer test called an enzyme-linked immunosorbent assay (ELISA) uses anti-IgE antibodies that are linked to an enyzme. A test called the CAP-RAST measures the amount of IgE in the blood that is specific for a given food.

Attempts are being made to directly measure immune system mediators such as histamine, eosinophil cationic protein (ECP), and mast cell tryptase. Electrodermal testing or electro-acupuncture allergy testing has been used in Europe, but is somewhat controversial and has not been approved by the U.S. Food and Drug Administration (FDA). An electric potential is applied to the skin and changes in the electrical resistance are measured upon exposure to the suspected allergen.

Procedures

Elimination diets are often used to diagnose food allergies. Suspect foods may be sequentially eliminated from the diet. Alternatively, after several weeks on a diet lacking any of the suspected allergenic foods, each suspected food is reintroduced one at a time and the patient is observed for signs of allergic reaction.

Treatment

Traditional

The most effective allergy treatment is avoiding all allergen exposure. This is usually possible with food allergens but can be very difficult with other types of allergens. Therefore immediate hypersensitivity reactions are usually treated with drugs. Immunotherapy, usually called allergy shots or desensitization, alters the balance of antibody types in the body.

Immunotherapy is generally used when medications cannot relieve symptoms. Extracts of the allergen are injected into the skin in gradually increasing amounts over a period of weeks, months, or years, with occasional booster shots. The amounts of allergen are too small to trigger an allergic response; however patients are monitored closely after each injection because of the small risk of anaphylaxis. Immunotherapy is most effective for hay fever and insect sting allergies, particularly in patients who cannot avoid allergens in the environment and who do not respond to medications. It may also reduce or eliminate the need for medications. While many rhinitis sufferers have been helped by allergy shots, they are costly and time-consuming and are not always effective. It may take up to several years of treatment to fully benefit from immunotherapy and about one in five patients do not respond at all. However some experts recommend preventative immunotherapy for children who have severe reactions to insect stings.

Drugs

There are a large number of prescription and overthe- counter medications for treating immediate hypersensitivity reactions. Most of these work by decreasing the ability of histamine to provoke symptoms. Other drugs counteract the effects of histamine by stimulating other systems or by reducing the general immune response. Medications are available as pills, liquids, nasal sprays, eye drops, and skin creams. The appropriate medication depends on the symptoms and the patient’s overall health. A physician may recommend trying a few different medications to determine which ones are most effective with the fewest side effects.

Antihistamines are the most common treatment for rhinitis. They block the histamine receptors in nasal tissue, thereby decreasing the effects of histamine released by mast cells. Antihistamines can be used after symptoms appear, although they may be even more effective when used preventively, before symptoms appear. They help reduce sneezing, itching, and runny nose (rhinorrhea). Antihistamines can also be used to treat other types of allergies.

There are a wide variety of antihistamines available. Older first-generation antihistamines often cause drowsiness as a major side effect. They can also cause dizziness, dry mouth, tachycardia, blurred vision, constipation, and a lowered threshold for seizures. Their effects can be similar to those of alcohol and care should be taken when operating motor vehicles, since individuals may not be aware that they are impaired. These antihistamines include:

• diphenhydramine (Benadryl and generics)
• chlorpheniramine (Chlor-trimeton, Piriton and generics)
• brompheniramine (Dimetane and generics)
• clemastine (Tavist and generics)

Newer antihistamines that do not cause drowsiness or cross the blood-brain barrier include:

• loratidine (Claritin, Clarityn)
• cetirizine (Zyrtec, Zirtec)
• fexofenadine (Allegra, Telfast)
• desloratadine (Clarinex, NeoClarityn)
• azelastin HCl (Astelin)
• astemizole (Hismanal)

Seldane (terfenadine), the original non-drowsy antihistamine, was voluntarily withdrawn from the market by its manufacturer in early 1998 because of its potential for causing serious heart arrhythmias and the availability of the equally effective but safer drug fexofenadine. Hismanal also has the potential for causing heart arrhythmias when taking more than the recommended dose or taking it along with the antibiotic erythromycin, the antifungal drugs ketoconazole or itraconazole, or the antimalarial drug quinine.

Decongestants constrict the blood vessels in the nasopharyngeal and sinus mucosa, reducing swelling and relieving nasal and sinus congestion. Both oral systemic preparations and nasal sprays—which are applied directly to the nasal lining—are available. Decongestants are stimulants and may cause increased heart rate and blood pressure, headaches, insomnia, agitation, and difficulty emptying the bladder. Use of nasal decongestants for longer than several days can result in loss of effectiveness and rebound congestion in which nasal passages become even more swollen.

Cromolyn sodium (sodium cromoglicate), In is a nonsteroidal mast cell stabilizer that prevents the release of mast cell granules and thus the release of histamine and other chemicals. It can be started several weeks before the onset of the allergy season as a preventive treatment. It can also be used for year-round allergy prevention. Cromolyn sodium is available as a nasal spray that coats the nasal membranes to treat allergic rhinitis and in aerosol form (a suspension of particles in gas) for asthma.

Newer types of allergy medications include:

• the IgE modifier omalizumab (Xolair), which interferes with the action of mast cells
• leukotriene modifiers or antileukotrienes, which block the action of leukotrienes—inflammatory substances released by the immune system during an allergic reaction—and include zafirlukast (Accolate), montelukast (Singulair), and zileuton (Zyflo)
• immunomodulatory topical ointments—which interfere with cell mechanisms that produce inflammatory responses—and include pimecrolimus (Elidel cream) and tacrolimus (Protopic ointment)

Corticosteroids help to prevent and treat the inflammation associated with allergic conditions by reducing the recruitment of inflammatory cells and the synthesis of immune-system chemicals called cytokines. Studies have shown that steroidal nasal sprays are more effective on an as-needed basis for seasonal allergies than antihistamines. Although hives and angioedema are usually treated with antihistamines, cromolyn, or epinephrine, intractable cases may be treated with oral cortisone; however it should be used sparingly and only as a last recourse because of its side effects. Corticosteroids are also used to prevent and control asthma attacks. Topical corticosteroids reduce mucous membrane and skin inflammations by decreasing the amount of fluid that moves from the vascular spaces into the tissues.

Topical corticosteroid creams are effective for contact dermatitis, although overuse can lead to dry and scaly skin. Moderately strong corticosteroids can be applied as a wrap for 24 hours. Short-term oral corticosteroid therapy also may be appropriate for acute contact dermatitis. Side effects are usually mild, but may include headaches, nosebleeds, and unpleasant taste sensations.

Because allergic reactions involving the lungs cause the airways or bronchial tubes to narrow, bronchodilators—which open or dilate the smooth muscle lining the airways—can be very effective for treating asthma attacks. Bronchodilators include:

• adrenaline (epinephrine)
• albuterol (Proventil)
• pirbuterol (Maxair)
• theophylline
• other adrenergic stimulants

Most bronchodilators are administered as aerosols. Theophylline, naturally present in coffee and tea, is usually taken orally, but in a severe asthma attack it may be administered intravenously.

Bronchodilators are often administered via metered-dose inhalers (MDIs):

• The inhaler is shaken and the patient exhales air from the lungs
• The inhaler is placed at least two fingerbreadths in front of the mouth and aimed at the back of the throat
• The inhaler is activated while breathing in slowly for three to four seconds
• The breath is held for at least ten seconds and then expelled
• There should be at least 30–60 seconds before the inhaler is used again
• The mouth should be washed out and the teeth brushed to remove residual medication

Other drugs, including steroids, are used in the long-term management of asthma and to prevent asthma attacks. The anticholinergics ipratropium bromide (Atrovent) and atropine sulfate are also used to treat asthma. Ipratropium is used in emergency situations with a nebulizer.

An anaphylaxis emergency is treated by injection of adrenaline, which relaxes muscles and helps open the airways. People who are susceptible to anaphylaxis because of food or insect allergies often carry an EpiPen—adrenaline in a hypodermic needle. Prompt injection into the thigh can prevent a more serious reaction. The patient should be placed in a recumbent position and vital signs—especially the airway status—determined. If the reaction is the result of an insect sting or injection, a tourniquet may need to be placed proximal to the penetrated area and released for one to two minutes at 10-minute intervals. If the individual does not respond to these interventions, emergency treatment is essential.

Alternative

Any alternative treatment for allergies starts with identifying the allergen and avoiding or eliminating it, although this is not always possible. A physician should be consulted before initiating any alternative therapy. Although alternative remedies may be derived from natural sources, they are still drugs and can have potentially harmful effects.

The following treatments may help relieve symptoms of allergic rhinitis from airborne allergens:

• Traditional Chinese medicine treats allergic rhinitis with various herbs. The patent combination medicines Bu Zhong Yi Qi Wan (Tonify the Middle and Augment the Qi) and Yu Ping Feng San (Jade Windscreen) are used for preventing allergies. Bi Yan Pian (Rhinitis Infusion) is often prescribed for symptoms affecting the nose.
• Acupuncture may be as effective as antihistamine drugs in treating allergic rhinitis. It is also may strengthen the immune system.
• Vitamins A and E are antioxidants and help to promote normal functioning of the immune system.
• Coenzyme Q10 may help promote normal functioning of the immune system.
• Zinc may boost the immune system.
• Echinacea spp. may have anti-inflammatory activity and may boost the immune system.
• Astragalus membranaceus (milk-vetch root) may help strengthen the immune system.
• Vitamin C has antihistamine and decongestive activities.
• Stinging nettle (Urtica dioica) has antihistamine and anti-inflammatory properties. The usual dose is 300 milligrams (mg) four times daily.
• Grape (Vitis vinifera) seed extract has antihistamine and anti-inflammatory properties. The usual dose is 50 mg three times daily.
• The bioflavonoid hesperidin may act as a natural antihistamine.
• The dietary supplement N-acetylcysteine may have decongestive activity.
• The homeopathic remedies Rhus toxicodendron, Apis mellifica, Nux vomica, and Ferrum phosphoricum alternating with Kali muriaticum have decongestant activities when taken internally.
• Licorice (Glycyrrhiza glabra) has cortisone-like antiinflammatory activity, stimulating the adrenals and relieving allergy symptoms. It can be taken as a tea or in 100–300 mg capsules. Long-term use can result in sodium retention or potassium loss.
• Chinese skullcap (Scutellaria baicalensis) has bronchodilating activity, is an anti-inflammatory, and can help prevent allergic reactions. It is taken in combination with other herbs.
• The herbal remedies khellin (Ammi visnaga) and cramp (Viburnum opulus) bark have bronchodilating activity.
• Ginkgo biloba seeds are used in Chinese medicine for relief from wheezing and coughing. The bioflavonoids quercetin and hesperidin may help stabilize mast cells.
• Although Ephedra sinicia (ma huang in traditional Chinese medicine) has anti-inflammatory activity and has proven effective in treating allergies, ephedra should not be used because it can raise blood pressure, cause rapid heartbeat, and interfere with adrenal gland function. The supplement ephedra was banned from sale in the United States in April of 2004 because of severe health risks.

The following homeopathic remedies are taken internally:

• Marsh tea (Ledum) for itching insect bites
• Apis mellifica for bee stings and hives that are relieved by cold
• Poison ivy (Rhus toxicodendron) for hives that are relieved with heat and for poison ivy, oak, or sumac rashes
• Stinging nettle (Urtica urens) for hives
• Croton tiglium oil for poison ivy, oak, or sumac rashes
• Anacardium A qualified homeopathic practitioner should be consulted to match symptoms with the correct remedy.

Various Chinese herbal remedies may be effective in treating atopic dermatitis. A poultice (crushed herbs applied directly to the affected area) made of jewelweed (Impatiens spp.) or chickweed (Stellaria media) may soothe the skin. A topical cream or wash containing Calendula officinalis, a natural antiseptic and antiinflammatory agent, may help heal rash.

Home remedies

The basic home remedy for allergies is to avoid or eliminate the allergen. This may involve keeping dust under control by cleaning or using air filters, making adjustments in pet ownership, removing items such as feather pillows, and eliminating allergenic foods from the diet. Children with allergies to milk, eggs, fish, or apples who follow an oral desensitization procedure— in which they are exposed to allergenic foods in controlled, but increasing, doses—may develop resistance to the allergen.

Eczema is treated by keeping the skin lubricated with hypoallergenic lotions and gentle soaps. For extremely dry, sensitive skin, Cetaphil lotion may be used as a cleanser instead of soap.

Cold-water compresses and calamine lotion may help reduce the irritation of contact dermatitis. Hydrocortisone ointment or cream or similar preparations can help alleviate itching. Side effects of topical agents may include excessive drying of the skin.

Prognosis

There is no cure for allergies. Although most allergy symptoms can be successfully treated with medications, these cannot prevent future allergic reactions. Some allergies improve over time, but often they worsen. Although severe asthma and anaphylaxis can be life-threatening, learning to recognize and avoid allergy-provoking situations enables most people with allergies to lead normal lives.

Some children outgrow their allergies, meaning that the allergen no longer causes obvious symptoms. Children younger than three who are in danger of anaphylaxis from foods such as milk, eggs, wheat, or soybeans often outgrow their food allergies after several years. Children who develop food sensitivities after three years-of-age are less likely to outgrow them. Allergies to foods such as tree nuts, fish, and seafood are generally lifelong.

More than half of all asthmatic children outgrow the condition completely and another 10% improve to the point where they have only occasional asthma attacks as adults.

Prevention

Avoiding allergens is the first line of defense. By identifying allergens, most people can learn to avoid allergic reactions from food, drugs, and contact allergens such as poison ivy or latex. Many allergenic foods, such as peanuts, eggs, and milk, are used as ingredients in other foodstuffs. Since 2006 food manufacturers in the United States have been required to clearly state if a product contains any of the eight major food allergens that are responsible for more than 90% of allergic food reactions: milk, eggs, peanuts, tree nuts, fish, shellfish, wheat, and soy.

Airborne allergens are more difficult to avoid. Recommendations include:

• avoiding environmental irritants such as tobacco smoke, perfumes, household cleaning agents, paints, glues, air fresheners, and potpourri
• controlling dust mites with allergen-impermeable covers on mattresses and pillows, frequent washing of bedding in hot water, and removal of items that collect dust such as stuffed toys
• vacuuming often
• keeping windows and doors closed to prevent pollen from entering the home
• reducing growth of mold by lowering indoor humidity, repairing foundations to reduce indoor leakage and seepage, and installing exhaust systems to ventilate areas where steam is generated, such as the bathroom and kitchen reducing pet dander,
• avoiding pet allergens including those in saliva, body excretions, pelts, urine, and feces, and restricting pets to only specific areas of the home
• repairing poorly vented gas and wood-burning stoves and artificial fireplaces because nitrogen dioxide from these has been linked to poor asthma control

Infants appear to be most sensitive to allergens during the first six months of life. Some physicians believe babies are especially vulnerable to allergies because their immune systems are still developing. Breastfeeding is recommended to reduce the likelihood of allergic reactions, since infants are never allergic to their mother’s milk. However traces of whatever the mother consumes pass into breast milk, so it is important to be alert to possible connections between a baby’s allergic symptoms and foods, medication, or even vitamins ingested by the mother.

Rashes in infants under one year of age are often caused by a food or drug allergy. Physicians often recommend that solid foods be introduced gradually if there is a family history of allergies. New foods can be introduced one at a time with 7–10 days in between. The later a food item is introduced into the diet, the less likely it is to cause an allergic reaction.

Babies and young children can have allergic reactions to ingredients in lotions, soaps, detergents, and baby wipes. Dye- and fragrance-free baby products can help prevent unnecessary exposure to potential allergens.

Toddlers are old enough to become anxious about allergy symptoms, which can trigger further allergic attacks and create a frustrating cycle. Parents should try to avoid conveying their own anxieties about allergy symptoms to the child.

During the preschool years, controlling a child’s diet and environment becomes more difficult. Children may feel stigmatized or left out when provided with special foods and denied others. Children also may begin encountering potential allergens, including pet dander, at school and playmates’ homes.

Parents of school-age children with allergies need to educate them about their condition and inform teachers and the school nurse of any restrictions and/ or emergency procedures. Children are generally not allowed to carry medication, asthma inhalers, or Epi-Pens in school, so arrangements must be made for the school nurse or other supervising adult to administer emergency medication.

Health care team roles

Diagnosis and effective management of allergy symptoms involves cooperation and collaboration between the patient and an interdisciplinary team of healthcare professionals. The primary-care physician or pediatrician, allergy and immunology specialists, nurses, laboratory technologists, respiratory therapists, and health educators are involved in helping patients and families learn to prevent and effectively manage symptoms. They teach patients how to distinguish mild allergy symptoms from those requiring immediate medical attention. Pharmacists and pharmacy assistants may offer additional instruction about medication use and the importance of adhering to prescribed treatment.

Key terms

Allergen—Any substance that provokes an allergic response.

Allergenic—Acting as an allergen or inducing an allergic response.

Allergic rhinitis—Inflammation of the mucous membranes of the nose and eyes in response to an allergen. Hay fever is seasonal allergic rhinitis.

Anaphylaxis—Severe, potentially fatal hypersensitivity caused by previous exposure to an allergen that can result in blood vessel dilation and a sharp drop in blood pressure, smooth muscle contraction, and difficulty breathing.

Angioedema—Severe non-inflammatory swelling of the skin, organs, and brain, possibly accompanied by fever and muscle pain.

Antibody—A specific immunoglobulin protein produced by the immune system in response to a specific antigen.

Antigen—A foreign protein or particle that causes the body to produce specific antibodies that bind to it.

Asthma—A lung condition, usually of allergic origin, in which the airways become narrow due to smooth muscle contraction, causing wheezing, coughing, and shortness of breath.

Atopic dermatitis—A skin condition resulting from exposure to airborne or food allergens.

Atopy—Genetic predisposition toward the development of allergies.

Conjunctivitis—Inflammation of the conjunctiva, the membrane covering the white part of the eye.

Contact dermatitis—Skin inflammation resulting from contact with an allergen or other substance.

Delayed hypersensitivity reactions—Allergic reactions mediated by T cells that occur hours to days after exposure to the antigen.

Eczema—An inflammatory skin condition characterized by redness, itching, and oozing lesions, which become crusty, scaly, or hardened.

Epinephrine—Adrenalin; a hormone released into the bloodstream in response to stress. Its many effects include stimulating the heart and increasing blood pressure, metabolic rate, and blood glucose concentration.

Granules—Small packets of reactive chemicals stored within cells.

Histamine—A chemical released by mast cells during an allergic reaction and which has a variety of effects on other cells.

Hives—A raised, itchy area of skin that is usually a sign of an allergic reaction. Immediate hypersensitivity reactions—Allergic reactions that are mediated by mast cells and occur within minutes of allergen contact.

Immunoglobulin E (IgE)—Antibodies produced in the lungs, skin, and mucous membranes that are responsible for allergic reactions.

Mast cells—A type of immune system cell that displays immunoglobulin E (IgE) on its cell surface and participates in allergic reactions by releasing histamine and other chemicals from intracellular granules. The lining of the nasal passages and eyelids are particularly rich in mast cells.

T cells—Immune system white blood cells that have highly specific antigen receptors on their surfaces. Some T cells stimulate other immune system cells to produce and release antibodies.