An allergy
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.