Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand,1997.
Dermographism is an exaggerated wealing tendency when the skin is stroked. It is the commonest form of physical or inducible urticaria. It is also called dermatographism, dermatographia and dermatographic urticaria.
In 25–50% of normal people firm stroking of the skin produces first a white line, then a red line, then slight swelling down the line of the stroke, and a mild red flare in the surrounding skin. In 5% of the population, this response is exaggerated enough to be called dermographism. In only a minority of these does it cause any symptoms.
The exact cause of dermographic urticaria is unknown. Histamine is the main chemical released by mast cells when the skin is stroked, but other chemical mediators may also be involved.
Some patients with severe dermographism may carry an autoantibody to some unknown cutaneous protein.
Dermographism can appear at any age, including children, but it is most common in young adults.
People with dermographism are usually otherwise healthy.
The onset of dermographism is usually gradual, but in some, the condition develops over a few days. Aggravating factors may include:
Once a few weals develop, subsequent scratching readily starts others in the vicinity.
General measures include avoiding the stimuli that set off bouts of itch, where possible. For example:
Antihistamines usually give good relief from symptoms. Non-sedating options include:
Antihistamines may need to be continued daily for at least several months; intermittent therapy is of less value.
Dermographism may also respond to phototherapy.
Dermographism may last for months or go on indefinitely. In many patients, however, it clears within a year or two, or at least the wealing is reduced to a degree which no longer causes significant symptoms.
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