Temperatures are rising, trees are blooming — in short, spring is here, and with it, so is allergy season.

Allergies in general — whether it be to food, pets or pollen — occur when the body’s immune system “sees a substance as harmful and overreacts to it,” according to the Asthma and Allergy Foundation of America.

And that is exactly what happens when pollen enters the body through the nose, eyes or mouth. The immune system mistakenly identifies it as a threat and triggers some of the well-known allergy symptoms: sneezing, runny nose and congestion, according to the Centers for Disease Control and Prevention.

Pollen causes various allergic reactions, such as symptoms of hay fever, and affects about 60 million people in the United States each year, according to the CDC.

For about a third of people in the U.S., pollen can also trigger “allergic conjunctivitis” which is an inflammation of the lining of the eye. Some of the symptoms include “red, watery or itchy eyes,” according to the agency.

“Most of the pollen that causes allergic reactions comes from trees, grasses and weeds,” according to AAFA. These plants make the tiny pollen grains that travel with the wind and enter through the eyes or nose.

“Flowering plants that spread their pollen by insects — like roses and some trees, like cherry and pear trees — usually do not cause allergic rhinitis,” the AAFA said.

What can you do to help your allergies?

Here are some ways to prevent allergic reactions to pollen, according to the AAFA:

• Ideally, you should start taking an allergy treatment before the pollen season starts.

• It’s best to limit outdoor time and keep windows closed when pollen counts are high.

• When you’re outside, wear sunglasses and cover your hair.

• Take a daily shower before going to bed and wash bedding in “hot, soapy water” weekly.

• Change and wash clothes worn outside.

The foundation also recommends tracking pollen counts — or how much pollen is in the air.

When is allergy season over? Technically, it never really ends.

Different allergy seasons stretch for much of the year, according to the Cleveland Clinic, a nonprofit academic medical center.

“Tree pollen season is usually at the beginning of spring in March, April and the first half of May while the grass pollen season is typically mid-May through early-to-mid-July,” Allergist-immunologist David M. Lang told the nonprofit. “And the ragweed season is usually from mid-August until that first frost.”

But the length — and intensity — of the pollen season depends on your location and the weather.

Climate change has also caused the seasons to get longer and caused higher pollen counts, AAFA reported.

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