DEAR MAYO CLINIC:

Is it possible to be allergic to snow? I have no allergies or problems in spring, summer or fall, but once snow starts falling, my eyes itch and I sneeze repeatedly. Why does this happen?

ANSWER:

In allergies, almost anything is possible. So you could be allergic to snow. But that would be very unusual. Much more likely, your symptoms are caused by another condition or a different allergy that's related to the snowy weather.

The most common cold-weather condition that can result in allergy symptoms is cold urticaria (sometimes called cold allergy or cold hives). In people who have this disorder, cold weather or low temperatures cause redness, itching, swelling and hives on the skin. These symptoms result from a histamine release in the body.

Histamine is a natural compound the body produces that's found in certain types of cells. Most histamine is contained within packets in these cells and is usually not released into the body. However, when an allergic response develops, histamine can be released from the packets. That release can cause a wide variety of symptoms, such as itching, skin welts, nasal congestion and, in some cases, even anaphylactic shock.

Another possible source of the problem may not be an allergy-related condition at all. Instead, it could be sunlight. Some people have a light-triggered reflex that causes sunlight to provoke sneezing or itchy eyes. During the winter months in cold climates, this reflex can be exaggerated by the light that's reflected off the snow, resulting in increased symptoms. In addition, cold temperatures can trigger the lining in your nose to produce excess mucus. That also can cause an increase in sneezing during the winter.

During spring and fall in particular, outdoor pollen commonly causes allergy symptoms. In the depths of winter -- especially in the Midwest and Northeast where temperatures are low and there's a blanket of snow -- there's very little outdoor pollen. But you still may have significant exposure to indoor allergy-causing substances (allergens) during this time. Because people in colder climates tend to stay indoors more often during the winter, allergic reactions to indoor allergens can significantly increase during the winter months. This is particularly true for homes with a heating or ventilation system that circulates air, because the allergens continually circulate in the air throughout the home, too.

Although we often think of allergies beginning in childhood, adults can develop new allergies. So I would recommend you see a doctor, preferably an allergist, for an evaluation of your symptoms and for allergy testing, which is usually done in one of two ways. The first is skin testing. The test involves placing drops of the material to be tested on the skin (typically on the arm or the back), poking the skin through the drop with a sharp instrument, and waiting about 15 minutes to see if redness and swelling develops at the site. The second method is a simple blood test. A blood sample is taken and then analyzed for allergy-producing antibodies.

Using the results of an allergy test, along with a review of your medical history and a physical exam, an allergist likely can help you find out if you have an allergy or other condition that may be triggered when the snow flies.

James Li, M.D., Ph.D., Allergic Diseases, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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