Allergies

Related Terms

Allergen, allergic, allergic reaction, allergic response, allergy, allergy shots, anaphylactic reaction, anaphylaxis, animal dander, antibodies, antibody, antihistamines, dander, decongestants, dust, dust mites, histamine, hives, hypersensitivity, immune, immune defense system, Ig, IgE, immune-mediated, immune response, immune system, immunoglobulin, immunoglobulin E, immunotherapy, inflammation, latex, molds, leukotriene inhibitors, pet dander, pollen, radioallergosorbent test, RAST, sensitized, sensitization, skin test, trigger, white blood cells.

Background

An allergy, or hypersensitivity reaction, occurs when the body's immune system overreacts to a substance that is normally harmless (allergen), such as mold, pollen, animal dander or dust mites. The white blood cells of an allergic individual produce an antibody called immunoglobulin E (IgE), which attaches to the allergen. This triggers the release of histamine and other inflammatory chemicals that cause allergic symptoms, such as runny nose, watery eyes and hives.
If the allergen is airborne, the allergic reaction will primarily affect the eyes, nose and lungs. If the allergen is ingested, the allergic reaction will primarily affect the mouth, stomach and intestines. If enough inflammatory chemicals are released, a reaction such as hives or rash could occur throughout the body. The most severe allergic reaction, known as anaphylaxis, can lead to low blood pressure, breathing difficulties, shock, and loss of consciousness, all of which can be fatal.
Allergies are extremely common, affecting more than 20% of Americans. The most common allergy triggers include pollen, dust mites, molds, animal dander, latex, foods and insect venom.
Allergy treatment depends on the type of allergy and severity of symptoms. Commonly used allergy medications include antihistamines, nasal sprays, decongestants, leukotriene inhibitors and allergen immunotherapy (allergy shots).

Author information

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

American Academy of Allergy Asthma & Immunology. .
Asthma and Allergy Foundation of America. Rhinitis and Sinusitis. .
Moffitt JE, Golden DB, Reisman RE, et al. Stinging insect hypersensitivity: a practice parameter update. J Allergy Clin Immunol. 2004 Oct;114(4):869-86.
National Institute of Allergy and Infectious Diseases. .
Natural Standard: The Authority on Integrative Medicine. .
Neugut AI, Ghatak AT, Miller RL. Anaphylaxis in the United States: an investigation into its epidemiology. Arch Intern Med. 2001 Jan 8;161(1):15-21.
The Cleveland Clinic Health Information Center. Allergy Overview. .

Causes

Most allergies are inherited, which means they are passed on to children by their parents. Although people inherit a tendency to be allergic, they may not inherit an allergy to the same allergen. When one parent is allergic, their child has a 50% chance of having allergies. That risk jumps to 75% if both parents have allergies.
Typically, an allergic response is not triggered the first time the body encounters the allergen. The first, or several times after the body is exposed to an allergen, the immune system becomes sensitized and prepares to react to the next encounter with the allergen. Once sensitized, the immune system can quickly detect the drug in the body and produce immunoglobulin E (IgE). These antibodies trigger the release of chemical mediators, including histamine, which may cause allergic symptoms up to and including anaphylaxis.
Common allergy triggers include pollen, dust mites, molds, animal dander, latex, foods and insect venom.

Symptoms

Common allergy symptoms include runny nose, tearing eyes, burning or itching eyes, red or swollen eyes, coughing, wheezing, difficulty breathing, hives, skin rash, stomach cramps, vomiting, diarrhea, headache and itchy nose, postnasal drip, impaired smell, as well as itchy mouth, throat or skin.

Diagnosis

Skin test: A skin test is used to determine whether a patient is allergic to certain substances, such as mold, dust mites or animal dander. During the test, the skin is exposed to different allergy-causing substances (allergens) and then observed for an allergic reaction. Some tests, like the percutaneous (puncture, prick or scratch) test, detect immediate allergic reactions, which develop within minutes of exposure to an allergen. Other tests, like the epicutaneous (patch) test, detect delayed allergic reactions that develop over the course of several days. If an allergen triggers an allergic reaction to a test, the patient will develop reddening, swelling or a raised, itchy red wheal (bump) that looks similar to a mosquito bite. The healthcare provider will measure the size of the wheal and record the results. The larger the wheal, the more severe the allergy.
Radioallergosorbent test (RAST): An allergen-specific immunoglobulin E (IgE) test, commonly referred to as radioallergosorbent test (RAST?) is a type of blood test that can help determine if a patient who experiences allergy symptoms, such as runny nose, watery eyes and hives, is allergic to particular substances called allergens.
The in vitro test (performed outside of the body, in a laboratory setting) exposes a blood sample to suspected allergens (like dust mites, pollen or animal dander) to determine whether the patient has developed allergen-specific immunoglobulin E (IgE) antibodies. Antibodies are proteins that recognize and bind to specific antigens.
During the procedure, a sample of blood is taken from the patient. The blood is then sent to a laboratory that performs specific IgE blood tests. An allergen-antigen complex is bound to an allergosorbent (paper disk) and the patient's blood is added. If the blood contains antibodies to the specific antigen, it will bind to the "tagged" immunoglobulins.
RAST? is less accurate than a skin test. However, if the patient has a severe skin disease (like eczema or psoriasis) that is present on large areas of skin on the arms or back, a skin test may not be possible. This is because the skin test may only be performed on the arms and back, and there may not be enough unaffected skin to perform a conclusive test. For these patients, an allergen-specific IgE test is the preferred diagnostic method.

Treatment

General: Allergy treatment depends on the type of allergy and severity of symptoms. Commonly used allergy medications include antihistamines, nasal sprays, decongestants, leukotriene inhibitors and immunotherapy (allergy shots).
Short-acting antihistamines: Short-acting antihistamines like diphenhydramine (Benadryl?) have been used to relieve mild to moderate allergy symptoms. Most short-acting antihistamines are available over-the-counter. These medications often cause drowsiness, and they have shown to blunt learning in children (even in the absence of drowsiness). However, loratadine (Claritin?), an over-the-counter medication, does not cause drowsiness or affect learning in children. Patients should consult their healthcare providers to determine whether these medications are safe for children.
Longer-acting antihistamines: Longer-acting antihistamines like fexofenadine (Allegra?) or cetirizine (Zyrtec?) are available by prescription for mild to moderate allergy symptoms. They cause less drowsiness than short-acting antihistamines, and they are equally effective. These medications do not usually interfere with learning. Patients should consult their healthcare providers to determine whether these medications are safe for children.
Nasal corticosteroid sprays: Nasal corticosteroid sprays can effectively relieve allergy symptoms in patients who are not responding to antihistamines. Commonly prescribed corticosteroid sprays include fluticasone (Flonase?), mometasone (Nasonex?) and triamcinolone (Nasacort AQ?).
Decongestants: Decongestants may help relieve symptoms such as nasal congestion (stuffy nose). These drugs shrink the tissues and blood vessels in the eyes and nose that swell in response to contact with an allergen. Nasal decongestant sprays like oxymetazoline (Afrin?) should not be used more than twice daily for three consecutive days because rebound nasal congestion may result. Decongestants in pill form do not cause this effect.
Cromolyn sodium: Cromolyn sodium is available as a nasal spray (Nasalcrom?) for treating hay fever. Eye drop versions of cromolyn sodium are also available for itchy, bloodshot eyes.
Leukotriene inhibitors: Leukotriene inhibitors like montelukast (Singulair?) have been used to control allergic asthma and to help relieve seasonal allergy symptoms.
Immunotherapy (allergy shots): Allergen immunotherapy, also known as allergy shots, is often used to treat patients who suffer from severe allergies, or for those who experience allergy symptoms more than three months a year. Allergen immunotherapy involves injecting increasing amounts of an allergen to a patient over several months.

Integrative therapies

Strong scientific evidence:
Whey protein: Hydrolyzed whey protein formula may be effective in preventing some allergies. Additional research is needed before a conclusion may be made.
Use with caution when taken in combination with any other drugs, herbs, or supplements. Use with caution in people with diabetes, low blood sugar, low blood pressure, bleeding disorders, gastrointestinal disorders, in those taking agents to treat any of these conditions, or in those taking agents which lower cholesterol, affect the immune system, or are broken down by the liver. Use caution while operating heavy machinery. Avoid the use of excessive doses for long periods of time, and of non-approved sources in infant formula. Avoid if pregnant or breastfeeding, in people with known allergy or sensitivity to milk or milk products, and in those avoiding dairy products.
Good scientific evidence:
Bifidobacterium longum BB536: Research suggests that BB536 may reduce symptoms associated with Japanese cedar pollen (JCP) allergy. At this time, there is limited information available on other types of allergies. Additional research is needed in this area.
Use cautiously in people with decreased HDL ("good") cholesterol levels, in people taking drugs to alter the immune system, and in pregnant and lactating women. Avoid in people with known allergy or sensitivity to ingredients in probiotic supplements. There is currently a lack of scientific evidence on the use of BB536 during pregnancy or breastfeeding.
Bromelain: Bromelain may be a useful addition to other therapies used for sinusitis (such as antibiotics) due to its ability to reduce inflammation/swelling. Studies report mixed results, although overall bromelain appears to be beneficial for reducing swelling and improving breathing. Better studies are needed before a firm conclusion can be made.
Avoid if allergic to bromelain, pineapple, honeybee, venom, latex, birch pollen, carrots, celery, fennel, cypress pollen, grass pollen, papain, rye flour, wheat flour or other members of the Bromeliaceaefamily. Use cautiously with history of bleeding disorders, stomach ulcers, heart disease, liver disease or kidney disease. Use cautiously before dental or surgical procedures or while driving or operating machinery. Avoid if pregnant or breastfeeding.
Butterbur: Good scientific evidence suggests that butterbur may be effective for allergic rhinitis prevention in susceptible individuals. Comparisons of butterbur to prescription drugs, such as fexofenadine (Allegra?) and cetirizine (Zyrtec?), have reported similar efficacy. Additional studies are warranted before a firm conclusion can be made.
Avoid if allergic or hypersensitive to Petasites hybridus or other plants from the Asteraceae/Compositae family (like ragweed, marigolds, daisies and chrysanthemums). Raw, unprocessed butterbur plant should not be eaten due to the risk of liver or kidney, damage or cancer. Avoid if pregnant or breastfeeding.
Fermented milk: According to limited research, drinking fermented milk may help with allergies. Further research is needed in this area.
Use caution with a low-fat or low-cholesterol diet. Caution is advised when used in large amounts in pregnant and lactating women. Avoid in people with a known allergy or sensitivity to dairy.
Galphimia glauca: Human studies have shown that Galphimia glauca may reduce eye and nose irritation associated with hay fever and pollen allergy. However, these benefits may be due to the placebo effect. Further research is needed in this area.
Use cautiously in people who have ear, nose, and throat sensitivity, mental disorders, or nosebleeds. Use cautiously in people who are taking depressants or agents that may increase the risk of bleeding. Use cautiously if pregnant or breastfeeding. Avoid if allergic or sensitive to Galphimia glauca, its parts, or members of the Malpighiaceae family.
Nasal irrigation: Good scientific evidence suggests that nasal irrigation may effectively treat allergies and chronic sinusitis. Well conducted clinical study is needed to make a conclusion in this area. Nasal irrigation is generally well tolerated. Use cautiously with a history of frequent nosebleeds. If the irrigation liquid is hot, the nose may become irritated.
Probiotics: Use of probiotic Enterococcus faecalis bacteria in hypertrophic sinusitis (sinus inflammation) may reduce frequency of relapses and the need for antibiotic therapy.
Probiotics are generally considered safe and well tolerated. Avoid if allergic or hypersensitive to probiotics. Use cautiously if lactose intolerant.
Unclear or conflicting scientific evidence:
Acupuncture: There is currently insufficient available evidence on which to base recommendations for acupuncture in non-allergic rhinitis. However, studies suggest that it may offer possible benefits. Additionally, more studies are needed of stronger design to determine whether or not acupuncture offers benefit in sinusitis. Acupuncture should be avoided in patients with heart disease, pulmonary disease, infections, bleeding disorders, medical conditions of unknown origin, or neurological disorders. Pregnant women, the elderly, diabetics, people with a history of seizures, and those receiving radiation therapy and/or taking drugs increasing bleeding risks should also avoid acupuncture.
Applied kinesiology: Applied kinesiology is commonly used for food allergy diagnosis. However, there is conflicting scientific evidence as to whether applied kinesiology is an effective diagnostic tool. Further research is warranted before a firm conclusion can be drawn. Applied kinesiology techniques in themselves are generally considered to be safe. However, medical conditions should not be treated with AK alone, and should not delay appropriate medical treatment.
Aromatherapy: Despite widespread use in over-the-counter agents and vapors, there is not enough scientific evidence to recommend use of eucalyptus oil as a decongestant-expectorant (by mouth or inhaled form). The available studies are of poor quality, and have used combination therapies or 1,8-cineole (eucalyptol), which is a component of eucalyptus. Further studies are needed before a firm conclusion can be made.
Skin rash (dermatitis) from direct contact with various essential oils has been reported in humans, and skin irritation and allergies may develop with regular use. Peppermint and eucalyptus oils may burn the skin if applied at full strength. Severe skin sensitivity to light may occur. Aromatherapy vapors may irritate the eyes, and affect breathing. There are reports of agitation, drowsiness, nausea, and headache with the use of aromatherapy. Some oils may have toxic effects on the brain, liver and kidney; long-term use may also increase cancer risks. Caution is advised in people who are driving or operating heavy machinery. Essential oils may be toxic if taken by mouth, and should not be swallowed. Fragrances may contain unknown and potentially toxic contaminants. The use of these oils is discouraged during pregnancy, and infants and young children may be especially sensitive.
Black seed: Studies in patients with allergies found that black seed decreased allergic disease severity, slightly decreased plasma triglycerides (levels of fat within the blood), and slightly increased HDL cholesterol. The effect of black seed for allergies is still not clear and further study is required.
Avoid with a known allergy/hypersensitivity to black seed, its constituents, black seed oil, or to members of the Ranunculaceae family. Allergic contact dermatitis has been reported after topical use of black seed or the oil from the seed.
Cat's claw: It has been suggested that cat's claw may help treat respiratory diseases involving allergies. However, there is limited scientific evidence to support this claim. More well-designed trials are needed to determine whether cat's claw is a beneficial treatment. Avoid if allergic to cat's claw or Uncaria plants or plants in the Rubiaceae family such as gardenia, coffee, or quinine. Avoid with a history of conditions affecting the immune system (such as AIDS, HIV, some types of cancer, multiple sclerosis, tuberculosis, rheumatoid arthritis, lupus). Use cautiously with bleeding disorders or a history of stroke, or if taking drugs that may increase the risk of bleeding. Discontinue use two weeks before surgery/dental/diagnostic procedures with bleeding risk, and do not use immediately after these procedures. Cat's claw may be contaminated with other Uncaria species. Reports exist of a potentially toxic, Texan grown plant, Acacia gregii being substituted for cat's claw. Avoid if pregnant, breastfeeding, or trying to become pregnant.
Choline: Oral tricholine citrate (TRI) effectively relieved allergic rhinitis symptoms in limited available study. However, further research is needed before a firm conclusion can be made. Choline is generally regarded as safe and appears to be well tolerated. Avoid if allergic to choline, lecithin, or phosphatidylcholine.
Elderberry and elder flower: Elder may offer benefits for bacterial sinusitis, such as reducing excessive mucus secretion. Herbal preparations containing elder may result in less swelling of mucus membranes, better drainage, milder headache, and decreased nasal congestion. Cyanide toxicity is possible. Avoid if allergic to elder or to plants related to honeysuckle. Some reports exist of allergies from contact with fresh elder stems. Use caution with diabetes, high blood pressure or urinary problems, or with drugs used for any of these conditions. Use caution with anti-inflammatories, diuretics ("water pills" for high blood pressure), or laxatives. Avoid if pregnant or breastfeeding.
Ephedra: Preliminary study suggests that a nasal spray containing ephedrine, a chemical in ephedra, may help treat symptoms of nasal allergic rhinitis. Additional research is needed before a firm conclusion can be made.
The U.S. Food and Drug Administration (FDA) has collected more than 800 reports of serious toxicity, including more than 22 deaths. Avoid use in individuals younger than 18 years old. Avoid use for prolonged periods (longer than seven days) due to risk of abuse or toxicity. Discontinue use at least one week prior to major surgery or diagnostic procedures. Use cautiously with cardiovascular disease, including structural heart disease, arrhythmia, coronary artery disease, high blood pressure, cerebrovascular disease, or a history of stroke or transient ischemic attack. Use cautiously with depression, anxiety disorders, anorexia/bulimia, a history of suicidal ideation, insomnia, tremors, urinary retention, enlarged prostate, diabetes, kidney disease, glaucoma, thyroid disease, and peptic ulcer disease. Use cautiously with monoamine oxidase inhibitor (MAOI) or stimulant use. Avoid if pregnant or breastfeeding.
Eucalyptus oil: Despite widespread use in multiple over-the-counter agents and inhalation vapors, there is currently insufficient available evidence to recommend either for or against eucalyptus oil as a decongestant-expectorant (in oral or inhaled form). Avoid if allergic to eucalyptus oil or with a history of seizure, diabetes, asthma, heart disease, abnormal heart rhythms, intestinal disorders, liver disease, kidney disease, or lung disease. Use caution if driving or operating machinery. Avoid with a history of actue intermittent porphyria. Avoid during pregnancy or breastfeeding. A strain of bacteria found on eucalyptus may cause infection. Toxicity has been reported with oral and inhaled use.
Honey: Currently there is insufficient human evidence to recommend honey for the treatment of rhinoconjunctivitis. Poor quality study reported no benefit of the use of honey for the treatment of rhinoconjunctivitis. Further research is necessary before a firm conclusion can be made. Avoid if allergic or hypersensitive to honey, pollen, celery, or bees. Honey is generally considered safe in recommended doses. Avoid honey from the genus Rhododendron because it may cause a toxic reaction. Avoid in infants younger than 12 months of age. Use cautiously with antibiotics. Potentially harmful contaminants (like C. botulinum or grayanotoxins) can be found in some types of honey and should be used cautiously in pregnant or breastfeeding women.
Horseradish: Studies have indicated that some horseradish constituents have antibiotic activity. Clinical study has used a combination product that contained nasturtium herb and horseradish root to treat sinusitis. Although the treatment had similar results as the standard antibiotic therapy control, the effect of horseradish alone cannot be isolated due to the use of a combination product. Additional high-quality clinical studies are needed before a conclusion can be made. Avoid if allergic or hypersensitive to horseradish (Armoracia rusticana), its constituents, or members of the Brassicaceae family. Large oral doses may provoke allergic reactions. Use cautiously with clotting disorders, hypotension (low blood pressure), thyroid disorders, kidney disorders, kidney inflammation, gastrointestinal conditions, skin ulcers, and stomach ulcers. Use cautiously if taking anticoagulants or antiplatelets (blood thinning agents), antihypertensives (blood pressure-lowering agents), anti-inflammatory agents, or thyroid hormones. Use cautiously if undergoing treatment for cancer. Avoid medicinal amounts of horseradish if pregnant or breastfeeding, as glucosinolates from horseradish are considered a toxin that can be excreted through breast milk and may pose a toxicity hazard. Also, based on herbal textbooks and folkloric precedent, horseradish has been used to induce abortion.
Hypnotherapy, hypnosis: It has been suggested that hypnotherapy may be effective for allergies and may help treat hay fever. However, further research is necessary to determine whether it is an effective treatment. Use cautiously with mental illnesses like psychosis/schizophrenia, manic depression, multiple personality disorder or dissociative disorders. Use cautiously with seizure disorders.
Kiwi: Currently, data on the therapeutic benefit of kiwi as a preventative for lung and other respiratory problems is lacking. More research is warranted before a recommendation can be made. Avoid if allergic or hypersensitive to kiwi, latex, birch pollen, banana, chestnut, fig, flour, melon, poppy seeds, rye grain, sesame seeds, and related substances. Kiwi is generally considered safe when taken in amounts naturally found in foods. Use cautiously with anti-platelet drugs like aspirin, cilostazol, or clopidogrel. Use cautiously with hormone therapies or serotonergic drugs. Avoid if pregnant or breastfeeding because clinical trials testing safety in supplemental doses are currently lacking. The amount found in foods appears to be safe in most people.
Lactobacillus acidophilus: Limited available study suggests that the Lactobacillus acidophilus (L. acidophilus) strain L-92 (L-92) may be effective for the treatment of Japanese cedar-pollen allergy. Further research is needed to confirm these results. L. acidophilus may be difficult to tolerate if allergic to dairy products containing L. acidophilus. Avoid with history of an injury or illness of the intestinal wall, immune-disease, or heart valve surgery. Avoid with prescription drugs, such as corticosteroids, because of the risk of infection. Use cautiously with heart murmurs. Antibiotics or alcohol may destroy L. acidophilus. Therefore, it is recommended that L. acidophilus be taken three hours after taking antibiotics or drinking alcohol. Some individuals may use antacids, such as famotidine (Pepcid?) and esomeprazole (Nexium?), to decrease the amount of acid in the stomach one hour before taking L. acidophilus.
MSM: According to preliminary clinical study, MSM reduces symptoms associated with seasonal allergic rhinitis (SAR). However, larger controlled trials are needed to confirm these findings. Avoid if allergic or hypersensitive to MSM. Long-term effects of supplementation with MSM have not been examined. Avoid if pregnant or breastfeeding.
Onion: Research shows that topical application of an alcoholic onion extract significantly reduced responses to allergies. Although intriguing, more research is needed in this area to establish the efficacy and dosing of topical onion extracts. Avoid if allergic or hypersensitive to onion (Allium cepa), its constituents, or members of the Lilaceae family. Use cautiously with hematologic (blood) disorders, diabetes, hypoglycemia (low blood sugar), and hypotension (low blood pressure). Use cautiously if taking anticoagulants or antiplatelets (blood thinners). Avoid medicinal doses if pregnant or breastfeeding.
Perilla: Preliminary evidence suggests some benefit of perilla extract for seasonal allergies. Further clinical trials are required before conclusions can be made. Avoid if allergic/hypersensitive to perilla or members of the Lamiaciae/Labiatae family. Use cautiously with cancer, low HDL-cholesterol, and immune disorders. Use cautiously if taking NSAIDS or barbiturates. Avoid if pregnant or breastfeeding.
Probiotics: Only a few types and combinations of probiotics have been studied as a possible allergy treatment. They have been studied mostly in children, teenagers, and young adults. Further research is necessary before a firm conclusion can be made. Probiotics are generally considered safe and well tolerated. Avoid if allergic or hypersensitive to probiotics. Use cautiously if lactose intolerant.
Reflexology: Preliminary data suggests that self-applied reflexology may be as beneficial as self-applied nasal irrigation in the treatment of chronic sinusitis. However, data are insufficient for making definitive conclusions. More studies are needed. Avoid with recent or healing foot fractures, unhealed wounds, or active gout flares affecting the foot. Use cautiously and seek prior medical consultation with osteoarthritis affecting the foot or ankle, or severe vascular disease of the legs or feet. Use cautiously with diabetes, heart disease or the presence of a pacemaker, unstable blood pressure, cancer, active infections, past episodes of fainting (syncope), mental illness, gallstones, or kidney stones. Use cautiously if pregnant or breastfeeding. Reflexology should not delay diagnosis or treatment with more proven techniques or therapies.
Shea butter: Studies show that shea butter may have nasal decongestant effects. More research is needed before a conclusion can be made. Shea butter may be unsafe in patients taking anticoagulants (blood-thinners), and in those with latex allergies.
Sorrel: Research suggests that an herbal combination preparation containing sorrel, Sinupret?, may have beneficial effects in improving symptoms of sinusitis when used with antibiotics. It is not clear if these same effects would be seen with sorrel alone or what dose may be safe and effective. For allergic rhinitis, there is not enough evidence to make a conclusion at this time. More research of sorrel alone is needed. Avoid sorrel with a known allergy to sorrel or any of its constituents. Avoid large doses of sorrel because there have been reports of toxicity and death. Many tinctures contain high levels of alcohol and should be avoided when driving or operating heavy machinery. Sorrel formulations may cause nausea or vomiting when taken with the prescription drugs metronidazole (Flagyl?) or disulfiram (Antabuse?). Avoid if pregnant or breastfeeding.
Spirulina: Anti-inflammatory properties of spirulina may help improve symptoms of allergic rhinitis. However, further high-quality studies are needed to confirm these findings. Avoid if allergic or hypersensitive to spirulina or blue-green algae. Use cautiously with phenylketonuria (a genetic disorder of a liver enzyme that disrupts normal body functions), autoimmune diseases, bleeding disorders, diabetes, and osteoporosis. Use cautiously with products containing the blue-green algae species Anabaena spp., Aphanizomenon spp., and Microcystis spp.; in underweight patients or in those taking antiobesity agents or appetite suppressants; of if consuming a high-protein diet. Avoid in children or if pregnant or breastfeeding.
Stinging nettle: For many years, a freeze-dried preparation of Urtica dioica has been prescribed by physicians and sold over-the-counter for the treatment of allergic rhinitis. Clinical trials demonstrating statistical significance over placebo and/or equivalence with other available treatments are needed to support the use of nettle in the treatment of allergic rhinitis. Avoid if allergic or hypersensitive to nettle, the Urticaceae family or any ingredient of nettle products. Use cautiously with diabetes, bleeding disorders, and/or low sodium levels in the blood. Use cautiously with diuretics and anti-inflammatory drugs. The elderly should also use nettle cautiously. Avoid if pregnant or breastfeeding.
Thymus extract: Thymus extract may reduce allergy symptoms due to its potential immune stimulating effects. More clinical trials are required before recommendations can be made involving thymus extract for this use. Avoid if allergic or hypersensitive to thymus extracts. Use bovine thymus extract supplements cautiously due to potential for exposure to the virus that causes "mad cow disease." Avoid use with an organ transplant or other forms of allografts or xenografts. Avoid if receiving immunosuppressive therapy, with thymic tumors, myasthenia gravis (neuromuscular disorder), untreated hypothyroidism, or if taking hormonal therapy. Avoid if pregnant or breastfeeding; thymic extract increases human sperm motility and progression.
Vitamin E: Although thought to aid in reducing the nasal symptoms of allergic rhinitis, vitamin E intake may not be effective. Current evidence is limited, however, and more studies are needed before a firm conclusion can be drawn. Avoid if allergic or hypersensitive to vitamin E. For short periods of time, vitamin E supplementation is generally considered safe at doses up to 1,000 milligrams per day. Avoid doses higher than 1,000 milligrams a day. Avoid with retinitis pigmentosa (loss of peripheral vision). Use cautiously with bleeding disorders. The recommended dose of vitamin E for pregnant women of any age is 15 milligrams; for breastfeeding women of any age, the recommended dose is 19 milligrams. Use beyond this level in pregnant women is not recommended.
Fair negative scientific evidence:
Applied kinesiology: Applied kinesiology (AK) has been used for diagnosis of allergies, but scant research has been done in this area. There is preliminary evidence suggesting that AK is not a reliable means of wasp venom allergy diagnosis. There is currently insufficient evidence on which to base recommendations for or against use of AK in this application. Applied kinesiology techniques in themselves are considered to be safe. However, medical conditions should not be treated with AK alone, and should not delay appropriate medical treatment.
Grape seed: Grape seed has been used to treat immune system disorders due to its antioxidant effects. However, a well-designed human study of allergic rhinitis sufferers showed no improvement in allergy symptoms with administration of grape seed extract ingredients. Avoid if allergic or hypersensitive to grapes or other grape compounds. Use cautiously if taking blood thinners such as warfarin, aspirin, non-steroidal anti-inflammatory drugs (NSAIDS), or anti-platelet agents. Use cautiously with bleeding disorders or if taking drugs that may increase the risk of bleeding. Use cautiously with drugs processed using the liver's "cytochrome P450" enzyme system. Use cautiously with blood pressure disorders or if taking ACE inhibitors. Avoid with disorders that increase the risk of bleeding or with active bleeding disorders (stomach ulcers, bleeding into the brain, etc.). Avoid if pregnant or breastfeeding.

Prevention

Avoid substances that trigger allergic reactions. Patients who are allergic to pollen should remain indoors in the morning and evening when outdoor pollen levels are highest.
Keep windows closed, and use the air conditioner, if possible, in the house and car.
Do not dry clothes outside.
Avoid unnecessary exposure to other environmental irritants such as insect sprays, tobacco smoke, air pollution and fresh tar or paint.
Regularly wash the hands and face to remove pollen.
A humidifier may help remove some of the allergens out of the air.
Children who have been breastfed are less likely to develop allergies. In addition, a mother who avoids cow's milk, eggs, nuts and peanuts while breastfeeding may help prevent allergy-related conditions, such as eczema, in some children.
There is evidence that infants who are exposed to airborne allergens like dust mites and animal dander may be less likely to develop related allergies.
Individuals with a history of anaphylaxis should carry an autoinjectable epinephrine device (known as an EpiPen?) with them at all times.

Complications

Anaphylaxis is a rapid, immune-mediated (allergic), systemic reaction to allergens (like food, medication or insect stings) that the individual has previously been exposed to. Anaphylaxis is a medical emergency that requires immediate medical treatment, as well as follow-up care with an allergist or immunologist. Symptoms of anaphylaxis can vary from mild to severe and may be potentially life threatening. The most dangerous symptoms are low blood pressure, breathing difficulties, shock and loss of consciousness, all of which can be fatal. Epinephrine is a medication used to treat anaphylaxis. Administering the epinephrine as soon as possible improves the chances of survival and a quick recovery.
Individuals who have a history of anaphylaxis should carry an autoinjectable epinephrine device (EpiPen?) with them at all times. If symptoms of anaphylaxis appear after exposure to an allergen or medication, the patient uses the device to inject the epinephrine into his/her thigh. A trained family member or friend may help the patient administer the epinephrine, if necessary.

Types of allergic reactions

Allergic reactions can be classified into four immunopathologic categories using various classification systems. The Gell and Coombs allergic classification system is based on the immune system's response to the allergen, not on the severity of the reaction.
Type I: Type I allergic reactions involve immunoglobulin E (IgE), which is specific for a particular drug, antigen or other allergen that triggers the allergic reaction. The allergen binds to the immunoglobulin on specific immune cells called basophils and mast cells. This binding results in the release of chemicals that cause inflammation in the body (such as histamine, serotonin, proteases, bradykinin generating factor, chemotactic factors from immune cells, leukotrienes, prostaglandins and thromboxanes) within 30 minutes of exposure. These chemical mediators cause allergy symptoms, such as urticaria (hives), runny nose, watery eyes, sneezing, wheezing and itching. This type of allergic reaction is often seen with penicillin, latex, blood products and vaccines.
Type II: This classification is called a cytotoxic reaction because it involves the destruction of the host cells. An antigen associated with a specific cell initiates cytolysis (breakdown of the cell) by an antigen-specific antibody, such as immunoglobulin G (IgG) or immunoglobulin M (IgM). This reaction often involves blood elements, such as red blood cells, white blood cells or platelets. It often occurs within five to 12 hours of exposure to the allergen, which may include penicillin, quinidine, phenylbutazone, thiouracils, sulfonamides or methyldopa.
Type III: This category involves the formation of an antigen-antibody immune complex, which deposits on blood vessel walls and activates cell components called complements. This causes a serum sickness-like syndrome, involving fever, swelling, skin rash and enlarged lymph nodes, in about three to eight hours. It may be caused by a variety of allergens, including penicillins, sulfonamides, intravenous (IV) contrast media and hydantoins.
Type IV: This classification involves delayed cell-mediated reactions. Antigens on the allergen release inflammatory mediators within 24 to 48 hours of exposure. This type of reaction is seen with graft rejection, latex, contact dermatitis and tuberculin reaction.

Common triggers

Pollen: Each spring, summer and fall, plants release tiny particles called pollen into the air in order to reproduce. Pollen from plants, such as ragweed, can trigger allergy symptoms.
Dust: Dust mites are microscopic organisms that live in dust and in the fibers of household objects like pillows, mattresses and carpets. Dust mites prefer warm, humid areas. Household dust is a combination of potentially allergenic materials, including fibers from different fabrics, animal dander, bacteria, mold, fungus spores, food particles, bits of plants or other allergens.
Molds: Molds are parasitic, microscopic fungi (like Penicillium) that have spores that float in the air like pollen. Mold is a common trigger for allergies, and it is usually found in damp areas, such as the basement or bathroom, as well as outside in grass, leaf piles, hay or mulch. In some people, symptoms of mold allergy may be triggered or worsened after eating certain foods, such as cheese processed with fungi. Mold spores peak during hot, humid weather.
Animal dander: Animals secrete oily fluids from their skin, which contain allergens. These fluids collect on fur, feathers and other surfaces inside the home. Proteins in the animal's saliva also cause allergic reactions. The allergens are capable of triggering reactions for several months. Allergies to animals can take two or more years to develop, and symptoms may not subside until months after discontinuing contact with the animal.
Latex: Latex, a substance found in products like rubber gloves or condoms, can also trigger allergic reactions in sensitive people. A component of the latex substance itself is an allergen. In addition, the latex glove powder residue is an airborne allergen that causes upper airway allergic reactions in some people. Latex reactions may cause a potentially life-threatening allergic reaction called anaphylaxis. According to the American Academy of Allergy Asthma & Immunology (AAAAI) about 220 cases of anaphylaxis and three deaths per year are attributed to latex allergies.
Foods: Food allergens are those parts of foods, usually proteins, which lead to allergic reactions. Most allergens can still cause allergic reactions even after they are cooked or have been digested. However, some allergens (usually from fruit and vegetables) only cause allergic reaction if eaten raw. These reactions are usually limited to the mouth and throat. According to the AAAAI, six foods, including milk, peanuts, soy, eggs, wheat and tree nuts (like pecans and walnuts), cause 90% of food allergies in children. Children usually outgrow allergies to milk, eggs and soy, but peanut, tree nut, fish and shellfish allergies continue throughout adulthood.
Insect venom: The honeybee, yellowjacket, paper wasp, white-faced hornet (bald-faced hornet) and fire ant are among the most common insects that trigger insect sting or bite allergies. Since the stinger is a modified egg-laying apparatus, only females can sting.