Hives

Hives, or urticaria, itchy skin condition characterized by the formation of welts with surrounding erythema (reddening) due to histamine release in the body's tissues. It is usually provoked by allergy to food, pollens, fungi, drugs, or parasites, but it may be symptomatic of infection, systemic disease, or emotional disorder. Dermographism is a condition in which slight skin pressure produces marked hives, like linear marks that appear after writing on the skin.