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Allergy
Hives2010.JPG
Hives are a common allergic symptom
SpecialtyImmunology
SymptomsRed eyes, itchy rash, runny nose, shortness of breath, swelling, sneezing[1]
TypesHay fever, food allergies, atopic dermatitis, allergic asthma, anaphylaxis[2]
CausesGenetic and environmental factors[3]
Diagnostic methodBased on symptoms, skin prick test, blood test[4]
Differential diagnosisFood intolerances, food poisoning[5]
PreventionEarly exposure to potential allergens[6]
TreatmentAvoiding known allergens, medications, allergen immunotherapy[7]
MedicationSteroids, antihistamines, epinephrine, mast cell stabilizers, antileukotrienes[7][8][9][10]
FrequencyCommon[11]

Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment.[12] These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis.[2] Symptoms may include red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling.[1] Food intolerances and food poisoning are separate conditions.[4][5]

Common allergens include pollen and certain foods.[12] Metals and other substances may also cause problems.[12] Food, insect stings, and medications are common causes of severe reactions.[3] Their development is due to both genetic and environmental factors.hypersensitivity of the immune system to typically harmless substances in the environment.[12] These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis.[2] Symptoms may include red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling.[1] Food intolerances and food poisoning are separate conditions.[4][5]

Common allergens include pollen and certain foods.[12] Metals and other substances may also cause problems.[12] Food, insect stings, and medications are common causes of severe reactions.[3] Their development is due to both genetic and environmental factors.[3] The underlying mechanism involves immunoglobulin E antibodies (IgE), part of the body's immune system, binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine.[13] Diagnosis is typically based on a person's medical history.[4] Further testing of the skin or blood may be useful in certain cases.[4] Positive tests, however, may not mean there is a significant allergy to the substance in question.[14]

Early exposure to potential allergens may be protective.[6] Treatments for allergies include the avoidance of known allergens and the use of medications such as steroids and antihistamines.[7] In severe reactions injectable adrenaline (epinephrine) is recommended.[8] Allergen immunotherapy, which gradually exposes people to larger and larger amounts of allergen, is useful for some types of allergies such as hay fever and reactions to insect bites.[7] Its use in food allergies is unclear.[7]

Allergies are common.[11] In the developed world, about 20% of people are affected by allergic rhinitis,[15] about 6% of people have at least one food allergy,[4][6] and about 20% have atopic dermatitis at some point in time.[16] Depending on the country about 1–18% of people have asthma.[17][18] Anaphylaxis occurs in between 0.05–2% of

Common allergens include pollen and certain foods.[12] Metals and other substances may also cause problems.[12] Food, insect stings, and medications are common causes of severe reactions.[3] Their development is due to both genetic and environmental factors.[3] The underlying mechanism involves immunoglobulin E antibodies (IgE), part of the body's immune system, binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine.[13] Diagnosis is typically based on a person's medical history.[4] Further testing of the skin or blood may be useful in certain cases.[4] Positive tests, however, may not mean there is a significant allergy to the substance in question.[14]

Early exposure to potential allergens may be protective.[6] Treatments for allergies include the avoidance of known allergens and the use of medications such as steroids and antihistamines.[7] In severe reactions injectable adrenaline (epinephrine) is recommended.[8] Allergen immunotherapy, which gradually exposes people to larger and larger amounts of allergen, is useful for some types of allergies such as hay fever and reactions to insect bites.[7] Its use in food allergies is unclear.[7]

Allergies are common.[11] In the developed world, about 20% of people are affected by allergic rhinitis,[15] about 6% of people have at least one food allergy,[4][6] and about 20% have atopic dermatitis at some point in time.[16] Depending on the country about 1–18% of people have asthma.[17][18] Anaphylaxis occurs in between 0.05–2% of people.[19] Rates of many allergic diseases appear to be increasing.[8][20][21] The word "allergy" was first used by Clemens von Pirquet in 1906.[3]

Many allergens such as dust or pollen are airborne particles. In these cases, symptoms arise in areas in contact with air, such as eyes, nose, and lungs. For instance, allergic rhinitis, also known as hay fever, causes irritation of the nose, sneezing, itching, and redness of the eyes.[22] Inhaled allergens can also lead to increased production of mucus in the lungs, shortness of breath, coughing, and wheezing.[23]

Aside from these ambient allergens, allergic reactions can result from foods, insect stings, and reactions to medications like aspirin and antibiotics such as penicillin. Symptoms of food allergy include abdominal pain, bloating, vomiting, diarrhea, itchy skin, and swelling of the skin during hives. Food allergies rarely cause respiratory (asthmatic) reactions, or rhinitis.[24] Insect stings, food, antibiotics, and certain medicines may produce a systemic allergic response that is also called anaphylaxis; multiple organ systems can be affected, including the digestive system, the respiratory system, and the circulatory system.[25][26][27] Depending on the rate of severity, anaphylaxis can include skin reactions, bronchoconstriction, swelling, low blood pressure, coma, and death. This type of reaction can be triggered suddenly, or the onset can be delayed. The nature of anaphylaxis is such that the reaction can seem to be subsiding, but may recur throughout a period of time.[27]

Skin

Substances that come into contact with the skin, such as latex, are also common causes of allergic reactions, known as contact dermatitis or eczema.[28] Skin allergies frequently cause rashes, or swelling and inflammation within the skin, in what is known as a "weal and flare" reaction characteristic of hives and angioedema.[29]

With insect stings a large local reaction may occur (an area of skin redness greater than 10 cm in size).[30] It can last one to two days.[30] This reaction may also occur after immunotherapy.[31]

Cause

Risk factors for allergy can be placed in two general categories, namely host and environmental factors.[32] Host factors include heredity, sex, race, and age, with heredity being by far the most significant. However, there have been recent increases in the incidence of allergic disorders that cannot be explained by genetic factors alone. Four major environmental candidates are alterations in exposure to infectious diseases during early childhood, environmental pollution, allergen levels, and dietary changes.[33]

Foods

The new version, the ImmunoCAP Specific IgE blood test, is the only specific IgE assay to receive Food and Drug Administration approval to quantitatively report to its detection limit of 0.1

The new version, the ImmunoCAP Specific IgE blood test, is the only specific IgE assay to receive Food and Drug Administration approval to quantitatively report to its detection limit of 0.1kU/l.[citation needed]

An allergist is a physician specially trained to manage and treat allergies, asthma and the other allergic diseases. In the United States physicians holding certification by the American Board of Allergy and Immunology (ABAI) have successfully completed an accredited educational program and evaluation process, including a proctored examination to demonstrate knowledge, skills, and experience in patient care in allergy and immunology.[137] Becoming an allergist/immunologist requires completion of at least nine years of training. After completing medical school and graduating with a medical degree, a physician will undergo three years of training in internal medicine (to become an internist) or pediatrics (to become a pediatrician). Once physicians have finished training in one of these specialties, they must pass the exam of either the American Board of Pediatrics (ABP), the American Osteopathic Board of Pediatrics (AOBP), the American Board of Internal Medicine (ABIM), or the American Osteopathic Board of Internal Medicine (AOBIM). Internists or pediatricians wishing to focus on the sub-specialty of allergy-immunology then complete at least an additional two years of study, called a fellowship, in an allergy/immunology training program. Allergist/immunologists listed as ABAI-certified have successfully passed the certifying examination of the ABAI following their fellowship.[138]

In the United Kingdom, allergy is a subspecialty of general medicine or pediatrics. After obtaining postgraduate exams (general medicine or pediatrics. After obtaining postgraduate exams (MRCP or MRCPCH), a doctor works for several years as a specialist registrar before qualifying for the General Medical Council specialist register. Allergy services may also be delivered by immunologists. A 2003 Royal College of Physicians report presented a case for improvement of what were felt to be inadequate allergy services in the UK.[139] In 2006, the House of Lords convened a subcommittee. It concluded likewise in 2007 that allergy services were insufficient to deal with what the Lords referred to as an "allergy epidemic" and its social cost; it made several recommendations.[140]

Low-allergen foods are being developed, as are improvements in skin prick test predictions; evaluation of the atopy patch test; in wasp sting outcomes predictions and a rapidly disintegrating epinephrine tablet, and anti-IL-5 for eosinophilic diseases.[141]

Aerobiology is the study of the biological particles passively dispersed through the air. One aim is the prevention of allergies due to pollen.Aerobiology is the study of the biological particles passively dispersed through the air. One aim is the prevention of allergies due to pollen.[142][143]