Dermatographic urticaria (also known as dermographism, dermatographism or "skin writing") is a skin disorder and one of the most common types of urticaria affecting 2â€"5% of the population.
Signs and symptoms
This weak membrane easily and rapidly breaks down under physical pressure causing an allergic-like reaction, in general a warm red wheal (welt) to appear on the skin. It can often be confused with an allergic reaction to the object causing the scratch, when in fact it is the act of being scratched that causes a wheal to appear. These wheals are a subset of urticaria (hives) that appear within minutes, in some cases accompanied by itching. The first outbreak of urticaria can lead to others on body parts not directly stimulated, scraped, or scratched. In a normal case, the swelling will decrease with no treatment within 15â€"30 minutes, but, in extreme cases, itchy red welts may last anywhere from a few hours to days.
Causes
Symptoms are thought to be the result of histamine being released by mast cells on the surface of the skin. Due to the lack of antigens, histamine causes the skin to swell in affected areas. If the membrane that surrounds the mast cells is too weak it will easily and rapidly break down under physical pressure, which will therefore cause an allergic-like reaction.
Symptoms can be caused or induced by
- stress
- tight or abrasive clothing
- watches
- glasses
- heat
- cold
- anything placing pressure on exposed skin
- infection
The underlying cause of dermatographism is not known, and can last for many years without relief. The condition may subside and be effectively cured; however, it is often a lifelong ailment. It is not a life-threatening disease and is not contagious.
Dermographism may occur in Mastocytosis (systemic mast cell proliferation).
Treatment
Dermographism can be treated by substances (i.e. an antihistamine) which prevent histamine from causing the reaction. These may need to be given as a combination of H1 antagonists, or possibly with an H2-receptor antagonist such as cimetidine.
OTC Vitamin C, 1000Â mg daily, increases histamine degradation and removal.
Not taking hot baths or showers may help if it is generalized (all over) and possibly for localized cases (in a specific area). If not taking hot showers helps, it may be a condition called shower eczema. If it affects mainly the head, it may be psoriasis. In rare cases, allergy tests may uncover substances the patient is allergic to.
While cromoglycate, which prevents histamine from being released from mast cells, is used topically in rhinitis and asthma, it is not effective orally for treating chronic urticaria.
See also
- Triple response of Lewis