Allergic rhinitis (hay fever) is an allergic reaction to tiny particles in the air called allergens. When you breathe in allergens through your nose or mouth, your body reacts by releasing a natural chemical called histamine. Several indoor and outdoor allergens cause hay fever. Common causes include dust mites, mold, pet dander and pollen from trees and plants.
Symptoms of hay fever include sneezing, nasal congestion and irritation of the nose, throat, mouth and eyes. Allergic rhinitis is not the same as infectious rhinitis, otherwise known as the common cold. Hay fever is not contagious.