Hives, also called uticaria, is an itchy skin condition characterized by the formation of weals with surrounding erythema, and due to histamine release. Hives is usually provoked by allergy to food (e.g., shellfish, nuts, fruits), pollen, fungi, drugs (e.g., penicillin), or parasites. But it may be symptomatic of infection, systemic disease, or emotional disorder.

Dermographism is a condition in which slight skin pressure may produce marked hives, as in the linear marks which appear after writing on the skin.