Known to most people as hay fever, allergic rhinitis is a very common medical problem affecting more than 15 percent of the population, both adults and children.

Allergic rhinitis takes two different forms: Seasonal and perennial. Symptoms of seasonal allergic rhinitis occur in spring, summer and/or early fall and are usually caused by allergic sensitivity to pollens from trees, grasses or weeds, or to airborne mold spores. Other people experience symptoms year-round, a condition called "perennial allergic rhinitis." It's generally caused by sensitivity to house dust, house dust mites, animal danders and/or mold spores.

Some people may experience both types of rhinitis, with perennial symptoms worsening during specific pollen seasons. As will be discussed later, there are also other causes for rhinitis.