Dermatitis herpetiformis (DH) is a skin condition where you get a very itchy rash. It is caused by intolerance to a food ingredient called gluten. It can be effectively treated with medication plus a gluten-free diet. DH is linked to a condition called coeliac disease, which is also caused by gluten intolerance. Treatment for both conditions is often needed.
What is dermatitis herpetiformis (DH)?
DH is a skin condition causing a very itchy rash. It is due to intolerance to gluten, which is a natural substance (a protein) found in certain foods. Gluten is in wheat, rye, and barley. Gluten intolerance also causes a gut condition called coeliac disease, which is closely linked to DH.
What causes dermatitis herpetiformis (DH)?
The cause is gluten intolerance. In this condition, your body reacts to gluten in food. Gluten intolerance is also sometimes called gluten sensitivity.
People with gluten intolerance have a kind of allergy to gluten, but it is not the same as a typical food allergy. With gluten intolerance, the gluten somehow triggers your body's immune system to react against the body's own organs. This is instead of doing what the immune system normally does, which is to be a defence against infections, etc. This may lead to various symptoms in different parts of your body. With DH, it is your skin which is affected.
It is not known exactly what causes the gluten intolerance in the first place.
Gluten intolerance also usually causes inflammation in the gut (in the small intestine). When this happens it is called coeliac disease. Most people with DH have some degree of coeliac disease. However, they may not have had any noticeable symptoms and their coeliac disease may not have been diagnosed. See separate leaflet called Coeliac Disease for more details.
The rest of this leaflet deals with DH.
Who gets dermatitis herpetiformis (DH)?
Around 1 in 1,000 people have DH. This compares with about 10 in 1,000 people in the UK having coeliac disease. Of 100 people with coeliac disease, about 17 will have DH. It is twice as common in men as it is in women and usually starts between ages 30-40 years, although it can occur at any age.
What are the symptoms of dermatitis herpetiformis (DH)?
There is an extremely itchy rash. It can affect any part of your skin, but is usually on your elbows, knees, buttocks and scalp. The rash is usually on both sides of your body at the same time (symmetrical). The rash has blisters and/or raised spots (papules) - but the blisters usually get scratched off to leave scabs. There may be burning or stinging on the area before the blisters start.
The rash can vary from week to week, but does not usually clear up without treatment.
You may also have symptoms of coeliac disease, such as tummy (abdominal) symptoms or unexplained tiredness. However, some people with coeliac disease have little in the way of symptoms, and DH may be the first sign of coeliac disease.
How is dermatitis herpetiformis (DH) diagnosed?
There are various skin conditions that cause itchy rashes with blisters, so a test is needed to diagnose DH for certain. The test is a skin biopsy. This involves taking a small sample of skin under local anaesthetic. The sample is examined under the microscope in a laboratory, using a special test to look for antibodies called IgA. This test can reliably diagnose DH.
If DH is suspected, you will usually be offered tests for coeliac disease as well. Blood tests can help to show if coeliac disease is likely. If the blood tests are positive, you may be offered a test on the gut (a biopsy to sample the lining of your bowel), which can confirm if you have coeliac disease.
How is dermatitis herpetiformis (DH) treated?
There are two treatments: diet and medication.
In the long term, a diet free of gluten will gradually reduce the DH symptoms, and may cure DH completely. (This diet also treats coeliac disease.) However, it can take months or years for the diet to improve DH. Therefore, medication is often needed to bring the skin symptoms under control. More information about the gluten-free diet is available from the leaflet about coeliac disease, and from Coeliac UK - see under 'Further help & information', below.
Medication helps control the rash quickly. The usual medication for DH is dapsone. Dapsone often stops the itching within two days. Dapsone may have side-effects, including anaemia. Therefore, regular check-ups and blood tests are needed while you are taking it.
Dapsone is used to treat certain skin conditions, including DH. Exactly how it works is not known. However, it seems to have anti-inflammatory and antibacterial actions. In DH, it is probably the anti-inflammatory action that is helpful.
If you cannot take dapsone or you have side-effects from it, other alternative medicines are available - for example, sulfapyridine.
Are there any possible complications?
Dermatitis herpetiformis (DH) itself does not usually cause complications. However, the gluten intolerance and coeliac disease, if untreated, may make you ill and have possible complications. Most of these problems can be prevented or treated by following a gluten-free diet, which treats both DH and coeliac disease.
What is the outlook (prognosis)?
Untreated, dermatitis herpetiformis (DH) tends to go up and down in severity, but usually continues.
With treatment, the outlook is very good, as DH clears up with medication and a gluten-free diet. Dapsone usually improves the rash quickly. The gluten-free diet takes longer to help - it may take a year or more to get the full benefit. About 8 in 10 people with DH have good results from the diet so they can either stop taking dapsone, or can reduce the dose.
Further help & information
Dr Naomi Hartree
Dr Louise Newson
Dr Helen Huins