They are produced by various physical stimuli such as heat, cold, sunlight, pressure, water, and exercise. Physical urticaria consists of brief attacks that usually last 30 to 60 minutes. Cholinergic urticaria is the most common type of physical urticaria. Dermatographism results from rubbing or stroking the skin. A variant of dermatographism is delayed pressure urticaria.
Cold urticaria develops in response to cold exposure.
Cold urticaria is normally mild but may be severe. Solar urticaria is a rare condition in which hives develop following exposure to natural or artificial light. Exercise-induced anaphylaxis is the most dangerous physical urticaria. It can be dramatic and life-threatening. Urticaria Caused by Systemic Disease Urticaria has been associated with systemic disease although it is rarely the sole presenting symptom.