The onset is usually gradual, but in some the condition develops over a few days. People with dermographism are usually otherwise healthy. Occasionally patients may have thyroid disease. Many authors have noted there is an important nervous factor. Attacks of itching and subsequent weals from scratching occur at intervals and may be related to agitation and worrying situations.
Symptoms are often worse in hot conditions, for example, after a warm bath.
Minor pressure from clothing, chair seats, working with various tools, clapping the hands or energetic kissing, etc., may start up the weals. They may develop after exercise if it is accompanied by knocks or pressure on the skin such as in rugby, wrestling or boxing. Towelling after bathing may start weal production. Once a few weals develop, subsequent scratching readily starts others in the vicinity. The weals are usually on the surface but some deep extension may occur and giant weals develop.