Dermatographism is a fairly common condition in which the skin is very sensitive to mechanical stimulation (like scraping or scratching over the skin). When this occurs, certain inflammatory cells under the skin surface release chemicals which cause redness and swelling that generally match the pattern of the mechanical stimulation (if you scratch in a long, straight line, you will get one long, straight hive, for example).
Unfortunately, there is no cure for dermatographism. Treatment involves trying to limit exposure of the skin to the sorts of things that cause you to break out in hives
. This could mean, for example, that you try to refrain from scratching yourself.
Additionally, for some people, typical anti histamine medications may be of some benefit. If taken regularly, they can help to reduce the severity of the skin reaction.
I recommend that you talk to either your primary care doctor
or an allergy doctor. They will be able to confirm the diagnosis of dermatographism and also help determine whether there are any additional treatments that might be of benefit to you. For example, in some cases that do not respond to anti histamines, there may be a role for sun or light therapy.