Allergy An allergy is an exaggerated reaction by the immune system in response to exposure to certain foreign substances. The response is exaggerated because these foreign substances are normally seen as harmless by the immune system in nonallergic individuals and do not cause a response in them.
In allergic individuals, the body recognizes the substance as foreign, and the allergic part of the immune system generates a response. Allergy-producing substances are called "allergens." Examples of allergens include pollens, dust mites, molds, animal proteins, foods, and medications. When an allergic individual comes in contact with an allergen, the immune system mounts a response through the IgE antibody. IgE is the allergic antibody. IgE is medically important for two reasons.
1- It mediate hypersensitivity ( Allergy/ anaphylactic).
2- It participate in host defense against certain parasites (such as helminths like Schistosoma mansoni, Trichinella spiralis, and Fasciola hepatica). The serum IgE level is usually increased in these infections. Because worms are too large to be ingested by phagocytes, they are killed by eosinophils that release worm-destroying enzymes. The other antibodies, IgG, IgM, and IgA, defend against infection. People who are prone to allergies are said to be allergic or "atopic." • Although many individuals outgrow allergies over time, allergies can also develop at any age, including during adulthood. • The environment plays a role in the development of allergy, as do genetics. There is a greater risk of developing allergic conditions if a person has a family history of allergy, especially in parents or siblings. hygiene hypothesis Many parents believe that their children must be kept in an environment that is as clean as possible, but some research suggests that being exposed to what many would call unclean conditions is good for a child's immune system. Research has indicated that children who are kept in very clean environments have a higher rate of hay fever, asthma and a wide range of other conditions. This is what is called the hygiene hypothesis #WhatIsAllergy #Allergens #howAllergyDevelop