What Are Allergies?

Allergies are caused by the body's overzealous reaction to normally harmless substances. Allergies can be triggered by pollen, animal dander, mold, dust, and insect droppings, or by certain foods or insect stings. Upper respiratory allergy symptoms include runny nose, itchy eyes, coughing, wheezing, and sneezing.

Featured Stories

My Doctor Misdiagnosed Me With Seasonal Allergies—but I Actually Had Lung Cancer That Spread to My Brain

At first, Gina Hollenbeck was told that her chronic cough was due to seasonal allergies, then a second doctor chalked it up to gastric reflux. It was a chest X-ray she insisted on paying for out of pocket that led to her terminal cancer diagnosis.
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More on Allergies

5 Causes of Hives You Wouldn't Expect

Those itchy, red welts can be brought on by more than just pet dander and pollen.
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What to Do When Allergies Cause a Sore Throat

When I get allergies, my symptoms are in the back of my throat, not my nose. Is that weird?
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College Student in Ohio Suffers Fatal Allergic Reaction to Milk Product

The 20-year-old was found dead holding his EpiPen after developing anaphylaxis.