Apologies for the delay in posting – last week was the end of term, deadline to submit grades for one college, then I flew out to Florida for a conference with other Anatomy and Physiology professors. Busy week!
One of my students did a short presentation after lab practicals were done describing her dermographism. While I videotaped a part of the excellent presentation (found below), this gives me a great opportunity to talk a little about this fascinating illness.
Dermographism is an allergy
Dermographism is officially known as “dermatographic uticaria” and affects 4-5% of the world’s population. Uticaria is also known as hives and is known for a burning sensation and pale, red, itchy bumps on the skin. Dermographism is this red, raised skin soon after rubbing or scratching in an area. My favorite source that you can’t cite, Wikipedia, says that it normally stays that way for about 30 minutes.
Cause and Treatment
It is thought the cause is from mast cells that have a weak membrane. So rubbing or scratching the skin will break the cell’s plasma membrane and release histamine, which will cause the allergic reaction in the area.
Because histamine is involved in these reactions, antihistamines are the treatment of choice. Sometimes both H1- and H2-antagonists are needed. Both of these drug classes block the histamine receptors. Cimetidine is an H2-antagonist often prescribed for dermographism. Chromoglycate is a drug known to block histamine from being released to start with, but is not effective when taken orally.