Dermatographia is a condition also known as skin writing. When people who have dermatographia lightly scratch their skin, the scratches redden into a raised wheal similar to hives. These marks usually disappear within 30 minutes.
The cause of dermatographia is unknown, but it can be triggered in some people by infections, emotional upset or medications such as penicillin.
Most people who have dermatographia don't seek treatment. If your signs and symptoms are especially bothersome, your doctor may recommend allergy medications such as diphenhydramine (Benadryl).