Allergy

Allergy, abnormal sensitivity to specific foreign material (an allergen). The allergy sufferer produces an antibody that combines with antigens, causing certain chemicals to be released, producing allergy symptoms. In the skin, this appears as eczema or urticaria (hives); in the nose and eyes, hay fever results; in the gastrointestinal tract, diarrhea may occur. In the lungs, there may be a spasm of the bronchi (airways), leading to the wheezing and breathlessness of asthma. Common allergens include drugs (penicillin, aspirin), foods (shellfish), plant pollens, animal furs or feathers, insect stings, and the house dust mite.