Hay fever, also known as rhinitis, is a type of allergy that affects approximately 20 percent of Americans. An allergic reaction occurs when the body mistakenly attacks allergens, and the immune system springs into action. Allergens are harmless compounds such as pollens, dust, molds and animal dander, but the body identifies them as foreign and therefore harmful, and launches a full attack on them.
The body forms antibodies, which signal the immune system to release chemicals such as histamine to attack the allergens. Excessive histamines in the body cause irritations like sneezing, coughing, runny nose and other allergy symptoms. Antihistamines, over-the-counter and prescription drugs are commonly used to treat hay fever. Allergies are not contagious.