Dermatitis herpetiformis (DH) is a severely itchy skin condition that often starts abruptly, affecting the elbows, knees, buttocks, scalp, and back. It usually starts as little bumps that can become tiny blisters and then are usually scratched off. DH can occur in only one spot, but more often appears in several areas.
The condition is related to IgA deposits under the skin. These occur as a result of ingesting gluten. These deposits take a long time to clear up, even when the patient is on a gluten-free diet.
It is unusual to develop DH after a celiac patient starts a gluten-free diet. About 5% of celiac patients will develop DH, either before being diagnosed or within the first year on the diet. The fact that DH can develop even after starting the diet is probably due to the long lasting nature of the IgA deposits.
For more information see the Dermatitis Herpetiformis page.