U.S. Department of Health and Human Services Public Health Service National Institutes of Health

Millions of Americans suffer from sneezing, coughing, itching, runny noses, and watering eyes when the pollen starts to fly. Each spring, summer, and fall tiny particles are released from trees, weeds, and grasses. These particles, known as pollen, hitch rides on currents of air. Although their mission is to fertilize parts of other plants, many never reach their targets. Instead, they make unscheduled detours into human noses and throats. At these sites, the pollen can trigger the allergic reaction that doctors call pollen allergy, or seasonal allergic rhinitis, and that many people know as hay fever or rose fever (depending on the season in which the symptoms occur).

Of all the things that can cause an allergy, pollen is one of the most pervasive. Many of the foods, drugs, or animals that cause allergies can be avoided to a great extent; even insects and household dust are not inescapable. However, short of staying indoors when the pollen count is high - and even that may not help - there is no easy way to evade windborne pollen. Yet there ARE some ways to ease the symptoms of hay fever - and scientists are working to find more and better approaches to allergy treatment.

The National Institute of Allergy and Infectious Diseases, a part of the National Institutes of Health, conducts and supports research on allergic diseases. The goals of this research are to provide a better understanding of the causes of allergy, to improve the methods for diagnosing and treating allergic reactions, and eventually to prevent them. This booklet summarizes what is known about the causes and symptoms of pollen allergy, as well as what medical researchers are doing to help people who suffer from it.

An allergy is a sensitivity to a normally harmless substance, one that does not bother most people. The allergen (the foreign substance that provokes a reaction) can be a food, dust particles, a drug, insect venom, or mold spores, as well as pollen. Allergic people often have a sensitivity to more than one substance.