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.
Dermatitis herpetiformis (DH) is a skin condition causing a very itchy rash. It is due to intolerance to gluten, which is a protein (a natural substance) found in certain foods. Gluten is in wheat, rye, and barley and sometimes in oats. Gluten intolerance also causes a gut condition called coeliac disease, which is closely linked to DH.
The cause is gluten intolerance which is the body reacting 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 the body's immune system to react against the body's own organs (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 the body. With DH, it is the skin which is affected.
We don't know 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 - although they may not have had any noticeable symptoms, and their coeliac disease may not have been diagnosed.
There is a separate leaflet called 'Coeliac Disease', explaining more about that particular condition. The rest of this leaflet deals with dermatitis herpetiformis.
Possibly around 1 in 1,000 people have DH. This compares with about 10 in 1000 people in the UK having coeliac disease. Of 100 people with coeliac disease, about 10 will have DH. It is twice as common in men as in women and usually starts between ages 15-40 years.
There is a very itchy rash. It can affect any part of the skin, but is usually on the elbows, knees, buttocks and scalp, and the rash is usually symmetrical (on both sides of the body at the same time). 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 abdominal (tummy) 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.
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 the intestine), which can confirm coeliac disease.
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, so 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 the Further information and help section below.
Medication helps control the rash quickly. The usual medication for DH is dapsone tablets. Dapsone often stops the itching within two days. Dapsone may have side-effects, including anaemia, so regular check-ups and blood tests are needed while you are taking it.
What is dapsone? Dapsone is a tablet that is used to treat certain skin conditions, including DH. We do not know exactly how it works, but 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 get side-effects from it, then other possible medicines are sulfapyridine tablets, sulphamethoxypyridazine tablets, colchicine tablets, azathioprine tablets, steroid creams (high-strength) or steroid tablets.
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.
Untreated, DH tends to go up and down in severity, but usually persists.
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.
3rd Floor, Apollo Centre, Desborough Road, High Wycombe, Bucks, HP11 2QW
Helpline: 0845 305 2060 Web: www.coeliac.org.uk
The charity for people with coeliac disease and dermatitis herpetiformis. Provides useful information about gluten-free diet.