Synonyms: dermatographism, dermatographia and dermatographic urticaria.
Dermographism is an exaggerated whealing tendency when the skin is stroked and usually presents as a sharply localized edema or wheal, with a surrounding erythematous flare occurring in seconds to minutes after the skin has been stroked.
Dermographism is the most common form of physical urticaria, followed by cholinergic urticaria. It may occur with other types of urticaria including those due to cold or pressure.
* 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 2-5% of the population this response is exaggerated enough to be called dermographism.
* The exact cause of dermographism is unknown. Histamine is the main chemical released by mast cells when the skin is stroked, but other chemical mediators may also be involved.
* Associations of dermographism:
1. Drug-induced urticaria (e.g. penicillin).
2. Thyroid disease (hypothyroidism and hyperthyroidism).
3. H2 blocker famotidine (Reported).
4. Infectious diseases (scabies or a worm infestation).
5. Diabetes mellitus
6. Onset of menopause.
Dermographism can appear at any age but is most common in young adults.
Once a few wheals develop, subsequent scratching readily starts others in the vicinity. These swellings die away rapidly and usually clear after half to one hour.
Triggering and exacerbating factors:
1. Nervous factor: attacks of itching and subsequent weals from scratching occur at intervals and may be related to agitation and worrying situations.
2. Hot conditions, for example, after a warm bath.
3. Minor pressure from clothing, chair seats, working with various tools, clapping the hands or energetic kissing, etc., may start up the weals.
4. They may develop after exercise if it is accompanied by knocks or pressure on the skin such as in rugby, wrestling or boxing.
5. Toweling after bathing may start weal production.
Course: Dermographism may last for months or go on indefinitely. In many patients, however, it clears within a year or two, or at least the whealing is reduced to a degree which no longer causes significant symptoms.
You should avoid triggering factors or conditions such as hot baths or showers, rough towelling down and rough clothing against the skin. Antihistamines often give good relief from symptoms. The non-sedating ones are generally preferred. The addition of an H2 antihistamine may be of benefit. Treatment may need to be continued regularly for at least several months; intermittent therapy is of less value.