About 10 to 20 percent of Americans suffer from allergic rhinitis. These hay fever types of allergies -- that is, allergies to airborne substances like tree pollen, mold spores, pet dander and dust mites -- are the result of an immune system malfunction. When sufferers breathe in something they're allergic to, their bodies go on red alert and send out antibodies to wage war. During the war, chemicals are released. One of them, histamine, is the one that causes all of the unpleasant symptoms of such allergies. The itching, sneezing, coughing and runny nose can be worse at some times than others, depending on your particular allergy.

For example, people who are allergic to tree pollen suffer the most in the spring, whereas people with allergies to grass pollen suffer more in the late spring and summer. Weed pollen -- especially ragweed -- is most problematic in the fall. And people with allergies to outdoor fungi and molds find their allergies are worst in late summer and early fall, although they feel their allergies from the end of March until November. Some types of allergic rhinitis last all year round without any season being worse than the others. Such allergies include sensitivity to dust mites or cockroaches, the dander -- dried skin and saliva -- of pets and the spores released from mold inside the house. These allergens are found all over the home, so they're hard to avoid. They can lurk in carpets, upholstery, beds and other fabric.

The other factor that comes into play with seasonal allergies is the weather. Pollen counts fluctuate according to temperature, humidity and wind. Pollen counts are at their highest on mornings that are warm and breezy with low humidity. Cold, rainy days are less likely to cause severe allergic reactions.