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Pollen, mold, pets, or dust mites? If your eyes are watering and your nose is stopped up, you’re probably more interested in what will stop your symptoms than what’s causing them. Knowing that, though, can help you get lasting relief.

If your allergies act up at certain times of the year, you may be allergic to pollen. In the spring, pollinating trees are usually to blame for allergies. In summer, grasses and weeds are the main culprits. In fall, it's weeds, especially ragweed.

If your symptoms tend to last all year, you may be allergic to dust mites, pet dander, or mold. Outdoors, mold usually peaks in late summer and early fall. But it can be around all year.

You can be allergic to several things. You can also have seasonal and year-round allergies. It’s common for people who have allergies to be allergic to more than one trigger.

Symptoms to Watch For

With allergies, your body sees the thing you’re allergic to as an "invader." It releases chemicals like histamine to fight the foreign substance.

Histamine is what causes your sinuses, nose, and mucus membranes to swell. You get congested, and your nose and eyes may itch and be watery. You probably sneeze a lot.

How Do I Find Out What Causes My Allergies?

Usually your doctor can diagnose allergies based on your symptoms and triggers. If your symptoms are more severe or medication doesn’t help, an allergist (a doctor who specializes in treating allergies) may do a skin test to find out what your triggers are.

She'll put tiny bits of potential allergens on your arm or back, and then scratch the surface of your skin. Any places that get red and itchy mean you have an allergy to that specific trigger.

Rarely, your doctor may also do a blood test to check for allergies.

Who Gets Outdoor Allergies/Hay Fever?

About 10% to 30% of people in the U.S. have outdoor allergies. Doctors don't know why some people have allergies and others don't.

If your parents have allergies, you're more likely to have them, too. If you have asthma or eczema, you're more likely to get hay fever or year-round allergies.

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