Dermatographism, also known as dermagraphism, simply translates "writing on the skin”. It is a very common localized hive reaction, affecting approximately 2-5% of the general population. This condition is characterized by the abrupt onset of welts and hives where the skin is exposed to pressure, scratching, itching or stroking. Dermatographism is frequently diagnosed incidentally, especially in relation to other skin disorders like eczema.

The skin lesions are believed to be the result of an inappropriate release of histamine in the absence of a typical immune signal. Histamine causes the exaggerated response leading to red welts and hives.

Clinically, dermatographism is transient; it manifests 5-7 minutes after irritation and usually fades or subsides within 15-30 minutes. The easiest way to elicit the physical findings is deliberate stroking of the skin. The hives in dermatographism typically occur in the same direction and orientation as the irritation. For example, scratching often produces distinct linear hives while direct pressure may lead to a more homogeneous broad looking hive. Other causes of dermatographism include exercise, heat, stress, vibration and cold exposure.

Diagnosis is usually based on clinical findings and corresponding history. If the diagnosis is in question, rubbing the skin with a tongue depressor can be used to elicit a reaction. In addition, a spring-loaded instrument, known as a dermographometer, can be used to measure skin sensitivity in response to a preset amount of pressure.

Treatment may be achieved with common dermatologic therapies. Over the counter anti-histamines can block the inappropriate histamine response while adequate skin care and routine moisturizing can improve dryness and itching. Finally cromolyn, a prescription medication, is used to stabilize the cell membrane responsible for the release of histamine and has a similar effect as anti-histamines.

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