Allergies

Synonyms

Hay fever

Definition

An allergy is the body’s exaggerated response to a foreign antigen (substance) or allergen that results in an immune response leading to a reaction such as allergic conjunctivitis (itchy eyes), allergic rhinitis (runny nose), anaphylaxis (allergic shock), asthma, atopic dermatitis, eczema, hives, serum sickness, or contact dermatitis (skin rash). The body makes antibodies (immunoglobins) that attach to foreign particles like allergens and viruses to allow the immune system to dispose of them. People who are allergic to a compound will make the immunoglobin type IgE in response to exposure to that compound. Common allergens include dust mites, animal dander, pollen, and foods. Allergic contact dermatitis is not mediated through IgE. While there is genetic predisposition to allergies, it requires a period of exposure (sensitization) for a person to make antibodies and develop symptoms. The production of antibodies in response to an allergen leads to allergic...