According to the National Oceanic & Atmospheric Administration, the vernal equinox -- otherwise known as the start of spring -- occurs at 8:07 p.m. EDT on March 20. Although the American College of Allergy, Asthma & Immunology (AAAAI) can't predict if the 2007 hay fever season will be mild or severe, allergists offered some tips to those leery of the sneezing fits that might await them.

Hay fever, also called allergic rhinitis, is an inflammation of the inner lining of the nose that occurs when an allergic person encounters an airborne allergen such as pollen, mold, dust mites or animal dander. Usually inhaled, these triggers generate allergy symptoms such as sneezing, coughing, runny nose, sore throat and itchy or watery eyes. According to the AAAAI, an estimated 20 percent of Americans have seasonal allergies.

Spring allergies are most commonly caused by tree and grass pollens. In the United States, trees generally pollinate February through May, grasses pollinate May through June, and flowering plants and weeds pollinate throughout the summer and until the first frost. But the severity of pollen circulation depends on a number of factors, including weather conditions, winds and geographic location. For instance, tree pollen season generally occurs in the southern third of the nation from January to June. But it is a problem in the middle third of the country and Northwest from February to June. The northern third typically has tree pollen alerts from March to June.

This year, some areas of the county experienced relatively mild winters while others took heavy hits of snow and ice. The experts say several factors can impact how people with allergies will fair in the coming months.

If your area experienced a mild winter, pollen counts are likely to increase because trees will probably pollinate earlier. Mild and warm weather during the spring months can also increase pollen counts.

If your area had a late freeze, pollen levels may decrease because those late season blasts of cold curtail tree pollen production. Heavy rains may have varying effects on the pollen count. Rain can reduce pollen levels initially, but then later cause increased pollen production through accelerated growth of grasses in the late spring and early summer. The AAAAI says rain the preceding fall or winter may cause increased tree pollen levels the next spring.

Windy areas may see an increase in pollen counts because the wind fans and spreads pollen over a wide area.

The AAAAI recommends the following precautions for people with hay fever:

• Avoid exposure to pollen by remaining indoors as much as possible during peak pollen count times. Keep windows closed in the home and car. Wear eyeglasses when outside and wash your hands or rinse your eyes after going indoors. Washing your hair after being outside for an extended period of time may also help reduce hay fever symptoms.

• Medication and eye drops may help relieve symptoms. Antihistamines, oral decongestants, anti-inflammatory nasal sprays and inhalers may be used to treat symptoms.

• Allergy shots may help relieve severe cases or decrease sensitivity to the allergen.

Copyright 2007 iVillage Total Health.