An allergy is a disorder caused
by an abnormal reaction to a harmless antigen in the environment. These
diseases include food allergies, hay fever, atopic dermatitis and allergic
asthma. Symptoms may include, a runny nose, shortness of breath, swelling red
eyes, or sneezing. Non-allergic individuals tolerate allergens without problems.
The two main types of allergic reactions are immediate hypersensitivity and delayed
hypersensitivity.
