Dermatitis herpetiformis (DH) is an intensely itchy, blistering skin rash that affects 15-25% of people with celiac disease. It is not known why some people with celiac disease develop the rash and others do not. This skin condition is not caused by herpes, despite the name.
The rash usually occurs on the elbows, knees, and buttocks. Many people with dermatitis herpetiformis do not experience the gastrointestinal (GI) symptoms of celiac disease, such as bloating, irregular bowel movements or weight gain/weight loss.
Dermatitis herpetiformis is usually a lifelong condition for those with celiac disease, but remission may occur.
The cause of dermatitis is the result of a hypersensitivity to gluten, a protein found in wheat and some other grains, such as bran. The gluten enters the blood stream and combines with an antibody called IgA (a part of the body’s immune system). Together they trigger inflammation and skin rash.
Most common allergies, such as hay fever and hives are triggered by IgE, a different type of antibody. These allergies can be treated with antihistamines and allergy shots (immunotherapy). Celiac disease and dermatitis herpetiformis do not respond to these treatments because they have a different underlying cause.
Dermatitis herpetiformis is diagnosed through blood tests and a skin biopsy.
If the antibody tests are positive and the skin biopsy has the typical findings of dermatitis herpetiformis, patients may not need to have an intestinal biopsy to confirm the diagnosis of celiac disease.
Both the skin disease and the intestinal disease respond to a gluten-free diet and recur if gluten is added back into the diet.
The rash can be controlled with antibiotics such as dapsone. Because dapsone does not treat the intestinal symptoms, people with dermatitis herpetiformis must maintain a gluten-free diet.
The dose of dapsone is usually slowly increased over time to reduce possible side effects. Dapsone may have adverse effects, so regular blood tests will be needed for the first three months.