A sensitivity to a specific substance, called an allergen , that is contacted through the skin, lungs, swallowing, or injection.
Allergic reactions are fairly common.
They occur more often in people with a family history of allergies . Most reactions happen soon after contact with an allergen . Most of these reactions are mild and can be treated at home. While first time exposure may only produce a mild reaction, repeated exposures may lead to more serious reactions. Allergic reactions vary.