Hives produced by rubbing, stroking, or friction on the skin; also known as dermographism. In dermatographism, histamine is released, causing capillaries (small blood vessels) to dilate, leading to redness and localized swelling. Dermatographism is a nonallergic cause of hives and is usually brought on by scratching. Long, raised, narrow, and itchy hives exactly follow the lines where stroking or scratching has occurred. Hives begin to appear on the skin immediately after the irritation and fade in less than an hour. Treatment is often unnecessary, but antihistamines are often prescribed if the hives cause extreme or persistent discomfort.