An itchy, blistering, burning skin rash, dermatitis herpetiformis (DH) is a difficult condition to live with. The rash and itching occur on the elbows, knees, scalp, back, and buttocks. This rash likely indicates a more serious underlying condition: an allergy to gluten. Dermatitis herpetiformis is also known as Duhring’s disease or gluten rash.
From the sound of the name, many people think this rash is caused by some form of the herpes virus. This is not true. Dermatitis herpetiformis occurs in people with celiac disease, which is an allergy or intolerance to gluten. Gluten is a protein found in wheat, rye, barley, and oats.
Fifteen to 25 percent of people with celiac disease (also called celiac sprue or gluten-sensitive enteropathy) have DH. Celiac disease can also cause intense abdominal pain, constipation, nausea, and vomiting. However, some people with DH have celiac disease but do not have any of the intestinal symptoms. Even without symptoms, intestinal damage occurs in 90 percent of people with DH.
The intestinal damage and rash is due to the reaction of gluten proteins with a special kind of antibody called IgA. Your body makes antibodies in response to infection or toxins. Sometimes, your body makes antibodies against food or environmental substances, such as pollen or dust mites. This is called an allergy.
Most allergies, such as hay fever and hives, are caused by the body’s reaction to an allergen, such as pollen, and the IgE type antibody. The body makes a lot more IgA type antibodies, found in the eyes, mouth, and lining of the intestines.
In the case of celiac disease, your body makes IgA antibodies to attack gluten proteins. This sensitivity to gluten is usually genetic, and so it runs in families. When IgA antibodies attack gluten, they damage the tiny villi structures in the intestines that allow you to absorb vitamins and nutrients.
The structures formed when IgA attaches to gluten and then enter the bloodstream. They begin to clog small blood vessels, especially those in the skin. White blood cells are attracted to these clogs. The white blood cells release a chemical called “complement” that causes an itchy, blistery rash.
Although more women than men are diagnosed with celiac disease, men are more likely to develop dermatitis herpetiformis than women. The rash usually begins in your teens or early 20s, though it can start in childhood. It is a lifelong condition, but may go into remission, even if you are still eating a diet high in gluten.
DH is one of the itchiest rashes possible. The rash almost always appears in the same place once a person develops it. Common locations include the elbows, knees, lower back, back of the neck, shoulders, buttocks, and scalp. The rash is usually the same size and shape on both sides of the body.
Before a full outbreak of the rash, you may feel the skin in a rash-prone area burn or itch. Pimple-like bumps start to form, filled with clear liquid. These are quickly scratched off. The bumps heal within a few days and leave a purple mark that lasts for weeks. But new bumps continue to form as old ones heal. This process can continue for years, or go into remission and return again and again.
DH is diagnosed with a skin biopsy, in which a small sample of skin is removed and examined under a microscope. Sometimes, a direct immunofluorescence test is done, in which the skin around the rash is stained with a dye that will show the presence of IgA antibody deposits.
Blood tests to check for these antibodies in the blood may also be done. An intestinal biopsy may be performed to confirm the presence of damage due to celiac disease.
DH can be treated with an antibiotic called dapsone. Dapsone is a powerful medicine with serious side effects. The dose must be increased slowly over several months before it is fully effective.
Most people see relief from taking dapsone. But side effects may include liver problems, sensitivity to sunlight, anemia, muscle weakness, and peripheral neuropathy. Dapsone may also have negative interactions with other medications, such as aminobenzoate potassium, clofazimine, or trimethoprim.
Other drugs that may be used include tetracycline, sulfapyridine, and some immunosuppressive drugs. These are less effective than dapsone.
The most effective and side effect-free treatment is strict adherence to a gluten-free diet. This means no food, drink, or medicines containing wheat, rye, barley, or oat products. Although this is difficult, it will have the most beneficial effect on your health if you have celiac disease. Any reduction in gluten intake may help lessen the amount of medication you will need to take.
Dermatitis herpetiformis is a lifelong disease. It may go into remission, but any time you are exposed to gluten, you may have an outbreak of the rash. Without treatment, DH and the underlying celiac disease can result in many negative health effects, including vitamin deficiencies, anemia, and gastrointestinal cancer.
Intestinal cancer is more likely in patients with untreated DH and celiac disease due to the constant inflammation in the intestines. Vitamin deficiencies and anemia may also be a problem due to intestinal malabsorption. Thyroid hormone deficiencies are also more common in patients with DH.