What are physical urticarias?
Physical urticarias occur in response to certain stimuli and occur only in those areas affected by those stimuli. The wheals tend to resolve within 2 hours.
Dermatographism is the most common physical urticaria. In dermatographism, wheals develop over parts of skin that are stroked firmly. Dermatographism isn't associated with any form of allergy or atopy, food, autoimmunity (where the body's immune system attacks parts of the body), or any other diseases.
Cholinergic urticaria is the second most common form of physical urticaria. Wheals form in response to exercise, stress, or emotions, and are surrounded by a reddened flare on the skin. Adrenergic urticaria, on the other hand, has wheals which are small and pink and surrounded by paler skin.
Delayed pressure urticaria develops on parts of the body which have had pressure applied to them for a long period of time. The wheals can develop after 30 minutes or even as long as 12 hours after the pressure has been lifted. Common areas are around the waist after wearing a tight pair of trousers or a tight belt, or at the ankles or lower leg where the top of socks are.
Other types of physical urticarias can occur in response to water, sunlight, cold, or pressure.
