Dermatographism (also called dermographism) describes skin reacts strongly with redness and swelling aftering being scraped or scratched. This may occur even after gentle stroking.
The phenomenon is sometimes referred to as "skin writing". It represents a type of hives (urticaria).
The skin may itch and appear with welts or raised patches.
The reaction is not caused by an allergy to the substance that touches the skin (as in contact dermatitis) but is a reaction to the physical impact of being touched.
Symptoms of Dermatographism
Red, linear hives appear in the areas where the skin has been scratched or rubbed, as if someone “wrote” on the skin (the term dermatographism literally means "skin writing"). The area may become itchy , leading to further scratching that triggers additional inflammation.
Dermatographism is most common in young adults but can appear at any age. Some people may experience these symptoms for only a few months, while others may experience dermatographism for years.
Image: Appearance of the word "Dermatographia" on a human arm 15 minutes after the letters have been traced with a blunt object on the skin.
Causes of Dermatographism
The symptoms are thought to be caused by an exaggerated immune response that releases histamine into the skin. Histamines cause the skin to swell up, turn red, and develop wheals (welts) in the affected areas. For unknown reasons, people with dermatographism release more histamine into the skin following otherwise normal skin contact.
Treatment of Dermatographism
Since most occurrences of dermatographism produce only mild symptoms that go away on their own, treatment is usually not necessary.
For persistent or bothersome cases, antihistamines can often provide relief.
Image: Courtesy of Wikipedia