Dermographism is a form of skin writing, which occurs in approximately 2-5% of the population. This is the most common form of physical urticaria and occurs when the skin is firmly stroked or rubbed. Capillary dilation produces an initial red line that is followed by arteriolar dilation resulting in broadening of the area. The final phase in this Triple Response of Lewis is the collection of fluid to form a wheal (Bajans call it a “whale”).
The exact cause and mechanism of dermographism is not known. Stroking of the skin results in the stimulation of mast cells and the subsequent release of histamine along with other inflammatory mediators in the affected area. Histamine causes the dilation of blood vessels making them leak fluids and also causes itching. Secondary causes include allergies to external agents like Penicillin, Scabies or worm infestation, insect bites and emotional upset. Patients with excessive mast cells (mastocytosis) can initially display skin writing tendencies early on as the disease progresses.
This condition can occur at any age but is more common in teenagers and young adults and there is no race or gender preference observed. Incidental trauma or pressure from chairs, rough collars/cuffs/seams, contact sports and towelling can be triggers. Hot environmental conditions, dry skin and any itchy dermatological condition e.g. eczema, can increase your risk.
Within 5-10 minutes of a stroking stimulus a tingling, itchy red swelling occurs which represents the area previously stroked. These individual raised wheals/hives usually last for about 30 minutes. Itching and whealing can affect the entire body but the scalp and genitals are less frequently involved. The sensation of perpetual and chronic itching can be very disconcerting and be a cause of severe emotional distress. The ability to create elaborate patterns on the skin as a form of body art can be intriguing to observers and even appear supernatural! When objects are used to write words on the skin they magically appear a few minutes later.
Your Dermatologist can easily make this diagnosis from a thorough history and even though it may not be present at your visit, a simple test can elicit the signs. This test involves using an orange stick or blunt object to elicit dermographism.
It is important to understand that this condition is not dangerous but more of a nuisance. Avoidance of trigger factors is imperative to reduce severity. Patients can be affected for a few weeks, months or years either continuously or at intervals. Antihistamines are very effective agents in the treatment of Dermographism. Phototherapy may be used in resistant cases.
The good news is it often resolves on its own.