Allergy

For the journal, see Allergy (journal).

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

Allergies, also known as allergic diseases, are various conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment.[11] These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis.[1] Symptoms may include red eyes, an itchy rash, sneezing, coughing, a runny nose, shortness of breath, or swelling.[12] Note that food intolerances and food poisoning are separate conditions.[3][4]

Common allergens include pollen and certain foods.[11] Metals and other substances may also cause such problems.[11] Food, insect stings, and medications are common causes of severe reactions.[2] Their development is due to both genetic and environmental factors.[2] 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.[3] Further testing of the skin or blood may be useful in certain cases.[3] Positive tests, however, may not necessarily mean there is a significant allergy to the substance in question.[14]

Early exposure of children to potential allergens may be protective.[5] Treatments for allergies include avoidance of known allergens and the use of medications such as steroids and antihistamines.[6] In severe reactions, injectable adrenaline (epinephrine) is recommended.[7] 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.[6] Its use in food allergies is unclear.[6]

Allergies are common.[10] In the developed world, about 20% of people are affected by allergic rhinitis,[15] about 6% of people have at least one food allergy,[3][5] and about 20% have or have had 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.[7][20][21] The word "allergy" was first used by Clemens von Pirquet in 1906.[2]

  1. ^ a b "Types of Allergic Diseases". NIAID. 29 May 2015. Archived from the original on 17 June 2015. Retrieved 17 June 2015.
  2. ^ a b c d Kay AB (2000). "Overview of 'allergy and allergic diseases: with a view to the future'". British Medical Bulletin. 56 (4): 843–64. doi:10.1258/0007142001903481. PMID 11359624.
  3. ^ a b c d e National Institute of Allergy and Infectious Diseases (July 2012). "Food Allergy An Overview" (PDF). Archived from the original (PDF) on 5 March 2016.
  4. ^ a b Bahna SL (December 2002). "Cow's milk allergy versus cow milk intolerance". Annals of Allergy, Asthma & Immunology. 89 (6 Suppl 1): 56–60. doi:10.1016/S1081-1206(10)62124-2. PMID 12487206.
  5. ^ a b c Sicherer SH, Sampson HA (February 2014). "Food allergy: Epidemiology, pathogenesis, diagnosis, and treatment". The Journal of Allergy and Clinical Immunology. 133 (2): 291–307, quiz 308. doi:10.1016/j.jaci.2013.11.020. PMID 24388012.
  6. ^ a b c d e "Allergen Immunotherapy". 22 April 2015. Archived from the original on 17 June 2015. Retrieved 15 June 2015.
  7. ^ a b c Simons FE (October 2009). "Anaphylaxis: Recent advances in assessment and treatment" (PDF). The Journal of Allergy and Clinical Immunology. 124 (4): 625–36, quiz 637–38. doi:10.1016/j.jaci.2009.08.025. PMID 19815109. Archived from the original (PDF) on 27 June 2013.
  8. ^ Finn DF, Walsh JJ (September 2013). "Twenty-first century mast cell stabilizers". British Journal of Pharmacology. 170 (1): 23–37. doi:10.1111/bph.12138. PMC 3764846. PMID 23441583.
  9. ^ May JR, Dolen WK (December 2017). "Management of Allergic Rhinitis: A Review for the Community Pharmacist". Clinical Therapeutics. 39 (12): 2410–2419. doi:10.1016/j.clinthera.2017.10.006. PMID 29079387.
  10. ^ a b "Allergic Diseases". NIAID. 21 May 2015. Archived from the original on 18 June 2015. Retrieved 20 June 2015.
  11. ^ a b c McConnell TH (2007). The Nature of Disease: Pathology for the Health Professions. Baltimore, MD: Lippincott Williams & Wilkins. p. 159. ISBN 978-0-7817-5317-3.
  12. ^ "Environmental Allergies: Symptoms". NIAID. 22 April 2015. Archived from the original on 18 June 2015. Retrieved 19 June 2015.
  13. ^ "How Does an Allergic Response Work?". NIAID. 21 April 2015. Archived from the original on 18 June 2015. Retrieved 20 June 2015.
  14. ^ Cox L, Williams B, Sicherer S, Oppenheimer J, Sher L, Hamilton R, Golden D (December 2008). "Pearls and pitfalls of allergy diagnostic testing: report from the American College of Allergy, Asthma and Immunology/American Academy of Allergy, Asthma and Immunology Specific IgE Test Task Force". Annals of Allergy, Asthma & Immunology. 101 (6): 580–92. doi:10.1016/S1081-1206(10)60220-7. PMID 19119701.
  15. ^ Wheatley LM, Togias A (January 2015). "Clinical practice. Allergic rhinitis". The New England Journal of Medicine. 372 (5): 456–63. doi:10.1056/NEJMcp1412282. PMC 4324099. PMID 25629743.
  16. ^ Thomsen SF (2014). "Atopic dermatitis: natural history, diagnosis, and treatment". ISRN Allergy. 2014: 354250. doi:10.1155/2014/354250. PMC 4004110. PMID 25006501.
  17. ^ "Global Strategy for Asthma Management and Prevention: Updated 2015" (PDF). Global Initiative for Asthma. 2015. p. 2. Archived from the original (PDF) on 17 October 2015.
  18. ^ "Global Strategy for Asthma Management and Prevention" (PDF). Global Initiative for Asthma. 2011. pp. 2–5. Archived from the original (PDF) on 20 November 2012.
  19. ^ Leslie C. Grammer (2012). Patterson's Allergic Diseases (7 ed.). Lippincott Williams & Wilkins. ISBN 978-1-4511-4863-3.
  20. ^ Anandan C, Nurmatov U, van Schayck OC, Sheikh A (February 2010). "Is the prevalence of asthma declining? Systematic review of epidemiological studies". Allergy. 65 (2): 152–67. doi:10.1111/j.1398-9995.2009.02244.x. PMID 19912154. S2CID 19525219.
  21. ^ Pongdee T. "Increasing Rates of Allergies and Asthma". American Academy of Allergy, Asthma & Immunology.