As April showers prepare to usher in May flowers, so too comes the tree, grass and weed pollens that trigger allergies in up to a quarter of the population.

While seasonal allergies are on the rise, heading them off early by seeking treatment before the runny nose, congestion and watery eyes set in can help keep these uncomfortable symptoms at bay.

"It's a lot easier to treat the allergic reactions before they start happening than to wait until you've had symptoms," says Andrew Singer, M.D., an allergist at the University of Michigan Health System . "Typically, this means starting a couple weeks before allergy season even begins to get your body ready for the onslaught of allergens. Once the allergic reaction happens, it takes more medication and it's much more difficult to calm things down and make you feel better."

Starting early means being ready any day now. Depending on what part of the country you live in, allergy season is likely to begin around March or April and continue right through the first frost in the fall. The earliest allergens to pop up are tree pollens, followed by grass pollens and then different types of weed pollens. Ragweed, one of the most common allergens, usually kicks up around late August or early September.

Twenty years ago, about 10 percent of the population experienced seasonal allergies, today that prevalence has doubled to 20 percent to 25 percent. Allergists notice this trend in perennial allergies and food allergies as well. Experts suspect the "hygiene hypothesis" is to blame for the upswing in allergies. As doctors have gotten better at treating infections with antibiotics and vaccines, children aren't exposed to as many infections as they were 20 to 30 years ago.

"The immune system literally gets bored," Singer says. "If one part of the immune system isn't challenged appropriately enough or with the right challenges at the right period of time, then it turns into more of an allergic immune system rather than an infection fighting immune system."

Allergies are most likely to spring up around age 2 or 3. They'll get worse as children get older and collect more allergens, but by the 20s or 30s, symptoms will tend to improve. As people continue to age, their reactions to allergens tend to lessen.

Of course, that's little consolation to someone who spends the spring sniffling and sneezing. Never fear: Many different medications are available to treat seasonal allergies. Traditional over-the-counter antihistamines can treat symptoms well but tend to make you drowsy. Newer antihistamines don't cause the same sort of drowsiness and tend to last 24 hours, which means taking a pill once a day as opposed to every four to six hours. Nasal steroid sprays are available by prescription. These effectively manage allergy symptoms without making you sleepy.

If medications don't work, allergy injections may be an option. Doctors determine exactly what's causing the allergy and create a customized injection of allergens based on the individual's sensitivities.

Allergy symptoms
• Sneezing
• Stuffy or runny nose
• Itchy nose, throat or ear canals
• Ear congestion
• Itchy, watery eyes
• Postnasal drainage
• Shortness of breath, especially with exercise or exertion
• Coughing
• Wheezing

Preventing allergy flare-ups
While allergies can't be cured, there are things you can do to limit your exposure to allergens:
• Avoid going outdoors during peak times of year for pollen exposure.
• Use air conditioning in your house and car and keep the windows closed.
• Wear a mask when doing lawn or garden work.
• Shower or bathe at night to remove pollens or other allergens from your hair and skin.
• Vacuum your carpets, curtains and soft furniture often.
• Remove any mold you find in your home.

For more information:
U-M Food Allergy Service
http://www.med.umich.edu/foodallergy/

UMHS Health Topics A-Z: Allergic rhinitis
http://www.med.umich.edu/1libr/guides/rhinitis.htm

UMHS Health Topics A -Z: Hay fever:
http://www.med.umich.e d u/1libr/aha/aha_hayfever_crs.htm

About allergies:
http://www.aaaai.org/patients/resources/fastfacts/allergies.stm

Controlling allergy symptoms:
http://familydoctor.org/083.xml