Dermatitis herpetiformis (DH) is an autoimmune skin condition linked to coeliac disease.
How many people have DH?
DH affects fewer people than coeliac disease, at around 1 in 10,000 people.
DH can appear at any age, but is most commonly diagnosed in those between the ages of 15 and 40.
It's more common in men than women and is rare in children.
People with DH can have:
- red, raised patches often with blisters that burst with scratching
- severe itching and often stinging
The rash can affect any area of the skin but is most commonly seen on the:
The rash usually occurs on both sides of the body, for example on both elbows.
Most people with DH will have the same kind of gut damage seen with coeliac disease, but may not complain of gut symptoms like:
Just over half (60%) of people with DH don't have gut symptoms.
DH is caused by the body's immune system reacting to a protein called gluten in foods containing wheat, barley and rye. This reaction causes a skin rash to develop.
A diagnosis of DH is confirmed by a skin test called a skin biopsy. A skin biopsy is a procedure where a sample of skin is removed to be tested.
What is involved in a skin biopsy?
During this test, a specialist skin doctor called a dermatologist will take a small sample of skin from an area without the rash. Samples of skin taken from the area with the rash don't always give an accurate result.
The skin sample is then tested. If you test positive for DH you'll be referred to a specialist gut doctor called a gastroenterologist to be tested for coeliac disease.
Diet before and during diagnosis
To ensure an accurate skin test is taken first time, it's important to keep eating gluten-containing foods before and during diagnosis.
If you've already removed gluten from your diet, you must reintroduce it in more than one meal every day for at least 6 weeks before having the tests.
The treatment for DH is a lifelong gluten-free diet.
A gluten-free diet is when all gluten-containing foods are removed from your diet
Gluten is found in wheat, barley and rye and sometimes people are sensitive to oats too.
A gluten-free diet should only start once a confirmed diagnosis of DH is given.
Find out how to live with a gluten-free diet
How long does treatment take to work?
The length of time it takes for the skin to heal varies from person to person but it can take up to 2 years or more.
Medication during treatment
Some patients will be given medication to help them over this period of recovery.
Medication will only be given to control the skin itching and blisters and doesn't treat any other symptoms.
The drug most likely to be used is called Dapsone.
Dapsone is taken in tablet form and must be swallowed.
It helps ease the itching and controls the development of blisters. It should work within a few days.
If you stop taking Dapsone before the gluten-free diet has taken effect, the rash will return.
Side effects of Dapsone
The most common side effect of Dapsone is anaemia.
Less common side effects are headaches and depression, while nerve damage is rare.
Because of these side effects, you'll always be prescribed the lowest effective dose. DH should be monitored once the drug dose has been reduced.
More information about this medicine is available in the Dapsone patient information leaflet.
Alternatives to Dapsone
Some people can't tolerate Dapsone. If you're one of these people, the following drugs can also be taken to clear the rash:
The same associated conditions and complications can occur in people with DH as in people with coeliac disease.
Some potential complications of DH include:
As with coeliac disease, the risk of developing these is reduced by following a gluten-free diet.
More about dermatitis herpetiformis
The British Association of Dermatologists (BAD) have produced a patient leaflet - Dermatitis Herpetiformis (gluten sensitivity) - which gives more information about this condition.