DEAR DR. DONOHUE: Is there such a thing as being allergic to cold? I think I am. When I go outdoors in the cold and then come back inside, I break out in hives. It doesn’t happen all the time, but it happens enough to make me wonder about it. What’s going on? – J.K.

ANSWER: Two body mechanisms are involved in the production of hives. Blood vessels close to the skin surface dilate and leak fluid, and that contributes to hive formation. In addition, mast cells, scattered in and beneath the skin, release histamine and other chemicals that promote the emergence of hives.

“Urticaria” is the medical name for hives. What you describe falls into a category of hives called physical urticarias. Among physical urticarias is dermatographism — hives that form in a line when the skin is stroked with a pencil or pen. Another example is pressure urticaria — hives that come when something presses on a part of the body. People with this kind of hives get them where the straps of a backpack weigh down on the skin. Another kind of hives is the urticaria that comes to some people when sunlight strikes them.

Cold exposure can also bring on an explosion of hives in sensitive people. Often the hives don’t appear until these people come in from the cold and begin to warm. You can test for cold urticaria by putting an ice cube on the forearm and leaving it there for four to 10 minutes. If you have cold urticaria, the place where the ice cube laid will have blanched and then develop a swelling and redness.

Taking an antihistamine before going out into the cold can sometimes prevent this reaction. If it doesn’t, the combination of an antihistamine along with cimetidine might do so. Cimetidine is used for heartburn control. It does have properties similar to antihistamines and can work in concert with them.

Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.