Dermatitis Herpetiformis

What is dermatitis herpetiformis?

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, barley and sometimes in oats.

Gluten intolerance also causes a gut condition called coeliac disease, which is closely linked to DH.

What causes dermatitis herpetiformis?

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 explaining more about coeliac disease. The rest of this leaflet deals with dermatitis herpetiformis.

Who gets dermatitis herpetiformis?

Possibly around 1 in 10,000 people in the UK have DH. This compares with about 1 in 100 people in the UK having coeliac disease. So only a small number of people with coeliac disease get DH.

DH usually starts between ages 15-40 years.

What are the symptoms of dermatitis herpetiformis?

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.

How is dermatitis herpetiformis 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 the intestine), which can confirm coeliac disease.

How is dermatitis herpetiformis 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, 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 section below.

Medication helps control the rash quickly. The usual medication for DH is dapsone tablets. Dapsone often stops the itching within 2 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 anti-bacterial 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 medication is sulfapyridine tablets, sulphamethoxypyridazine tablets, steroid creams (high strength) or steroid tablets.

Are there any complications of 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. See separate leaflet called 'Coeliac Disease' for more detail.

What is the outlook for dermatitis herpetiformis?

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, meaning they can either come off dapsone completely or can reduce the dose.

Further information and help

Coeliac UK

Suites A-D, Octagon Court, High Wycombe, Buckinghamshire, HP11 2HS
Helpline: 0870 444 8804
Web: www.coeliac.org.uk
The charity for people with coeliac disease and dermatitis herpetiformis. Provides useful information about gluten-free diet.