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Dermatographic urticaria is sometimes called "skin writing".
Dermatographic urticaria (also known as dermographism, dermatographism or "skin writing") is a skin disorder seen in 4–5% of the world's population and is one of the most common types of urticaria, in which the skin becomes raised and inflamed when stroked, scratched, rubbed, and sometimes even slapped.
The symptoms are thought to be caused by mast cells in the surface of the skin releasing histamines without the presence of antigens, due to the presence of a weak membrane surrounding the mast cells. The histamines released cause the skin to swell in the affected areas.
This weak membrane easily and rapidly breaks down under physical pressure causing an allergic-like reaction, in general a red weal (welt) to appear on the skin. It can often be confused with an allergic reaction to the object causing a scratch, when in fact it is the act of being scratched that causes a weal to appear. These weals are a subset of urticaria (hives) that appear within minutes, in some cases accompanied with 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 reduce itself with no treatment within 15–30 minutes, but, in extreme cases, itchy red welts may last anywhere from a few hours to days.
The underlying cause of dermographism is not known, and can last for many years without relief. Five percent of chronic cases are never solved. Increased incidence has been observed following prolonged exposure to microwaves. The condition may subside and be effectively cured; however, it is often a lifelong ailment. It is not a life-threatening disease nor contagious.
Symptoms can be induced or worsened by periods of anxiety, physical stress, tight or abrasive clothing, watches, glasses, heat, cold, or anything that causes stress to the skin.
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.
Not taking hot baths or showers may help if it is generalized (all over) and possibly for localized (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. Using biodegradable or hypo-allergenic soaps and laundry supplies may help.
Using menthol mixed with aqueous cream is often an excellent temporary solution to help reduce irritation and itching in a localised area.
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. Bug spray may also cause the reaction to the skin.
Frequent anecdotal evidence suggests taking in small amounts of alcohol may help with the itching, or temporarily cause the inflammation/welts to subside.
Acupuncture and Chinese herbs have long been used to treat urticaria in the Asian world. Results of clinical trials of both acupuncture and Chinese herbs are inconclusive and are possibly a result of the placebo effect, as the trials did not involve a control group.
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