Dermatographism is the most common form of physical inducible urticaria. It is characterised by a rapid reaction with the appearance of wheals (sometimes also referred to as “bumps” or “hives”) and redness following mechanical stimulation of the skin, for example through friction or pressure.
Red, itchy lines frequently appear on the skin in areas where the patient has scratched using their fingernails. It is estimated to affect approximately 2–5% of the general population, although only a minority experience symptom severe enough to seek medical attention. The more troublesome variants cause intense itching and wheals a few minutes after provocation, with symptoms that may last for more than 30 minutes, while asymptomatic cases usually consist of transient reddish wheals without itching.
Recent international epidemiological data have found higher rates in females and in patients aged between 25 and 60 years. Disease activity may be exacerbated by anxiety or by food intake (not by any specific food, but simply by the act of eating) and improved by physical exercise. A history of allergy or atopy, allergic rhinitis, asthma or thyroid disease is more common among affected individuals, and sensitisation to aeroallergens is also more frequent than in the general population. Quality of life may be significantly affected in severe cases.
As with other forms of urticaria, the underlying mechanism involves the activation of specialised white blood cells known as mast cells, which produce and release histamine. In most cases, it is difficult to identify the cause of this activation. Autoimmune diseases, chronic infections and alterations in the intestinal microbiota have been suggested as possible causes. This condition is not caused by food allergy.
The diagnosis of dermatographism is clinical and is confirmed by a simple provocation test (for example, rubbing the skin with a spatula or with a device specifically designed for this purpose). In general, no additional tests or laboratory investigations are required. First-line treatment consists of non-sedating antihistamines, with dose escalation up to four times the standard dose recommended for refractory cases. Dermatographism has a good prognosis and may last for several months or, in rare cases, years, but it does not result in sequelae or complications.
Content developed by Dr Pedro Silva, Immunoallergologist, HPA Health Group
27, February 2026
