Seborrhoeic Dermatitis
What is seborrhoeic dermatitis?
The words ‘dermatitis’ and ‘eczema’ mean the same thing and are interchangeable. This leaflet could just as easily have been called ‘seborrhoeic eczema’. For simplicity the word ‘dermatitis’ will be used here.
‘Dermatitis’ means an inflammation of the skin: ‘seborrhoeic’ simply means that the rash commonly comes up in areas rich in sebaceous (grease) glands such as the side of the nose, forehead and scalp.
Seborrhoeic dermatitis is harmless and very common, affecting as many as 3% of people. Infants can have it; but then it usually clears up over the course of a few months. It is common in young adults, peaks at the age of forty, and is less common in old age.
What causes it?
This is not fully understood. Seborrhoeic dermatitis does best with treatments that attack the yeasts that live on the surface of everyone’s skin. This suggests that these skin yeasts play a part in causing it. They are not the same as the yeasts that cause thrush or those that are present in foods.
Seborrhoeic dermatitis usually affects people who are otherwise well. However it is particularly likely to occur in people who have Parkinson’s disease, and can be severe in people who have a human immunodeficiency virus (HIV) infection, in whom the yeasts are able to grow unchecked. However seborrhoeic dermatitis itself is not passed from person to person.
Tiredness and stress can sometimes trigger a flare of seborrhoeic dermatitis. It is not related to diet. It is more common in cold than in warm weather.
Is it hereditary?
This is not known.
What are the symptoms of seborrhoeic dermatitis?
Seborrhoeic dermatitis can be itchy or sore. The redness of the rash can be embarrassing when it comes out on the face. Seborrhoeic dermatitis of the scalp can produce embarrassing dandruff.
What does it look like?
The rash is made up of red areas covered with greasy looking white or yellowish scales. Most commonly the rash comes up on just on one or two areas, but it can sometimes be extensive. It occurs most often:
On the scalp: seborrhoeic dermatitis here ranges from a mild dandruff to a redder, scalier, and sometimes oozy rash, which can extend out onto nearby parts of the forehead and around the ears. Cradle cap in infants may be part of a seborrhoeic dermatitis.
On the face: it often affects the inner parts of the eyebrows, the creases beside the nose and adjacent parts of the cheeks. The eyelids may also be red and irritable (blepharitis).
In and around the ears: some people have inflammation inside the ear canal, in the cup of the ear, and behind the ears. The skin often oozes and crusts in these areas, and the ears may swell up. Inflammation in the ear canal (otitis externa) can cause it to become blocked.
On the front of the chest and between the shoulder blades: it shows up as well-defined, roundish red patches that are sometimes scaly.
In the flexures: it often affects areas that are prone to sweating and retained moisture such as the skin under the arms and breasts, in the groins, or in folds on the abdomen. In infants, the nappy area is affected.
How is it diagnosed?
There are no tests that will prove that you have seborrhoeic dermatitis. Your doctor will make the diagnosis by the look of the rash, and where it lies on the skin. A skin biopsy is seldom needed.
The most common problem for doctors is telling whether the rash on your scalp is seborrhoeic dermatitis or psoriasis. Psoriasis of the scalp usually comes up in well-defined rather redder patches, with a whiter, thicker type of scaling. Sometimes the two seem to overlap. If there is any suspicion of scalp ringworm (a fungus infection), your doctor will send a specimen of the scales for culture
Can it be cured?
Treatment keeps seborrhoeic dermatitis under control, but does not get rid of it once and for all.
How can it be treated?
Remember that treatment suppresses seborrhoeic dermatitis rather than cures it, and that it often comes back after treatment has stopped. You may therefore have to use treatments for months or even years. For this reason, they must be safe in the long term. The choice of treatment also depends on which parts of the skin have the rash:
In the scalp: for dandruff, medicated shampoos containing agents such as zinc pyrithione, selenium sulphide or ketoconazole can be used regularly. Leave them on for 5 to 10 minutes before rinsing them off. If dense scales cover the scalp, remove these first with warm olive oil. Sometimes a scalp application containing a mild steroid can help reduce itching and redness. Alternatively a salicylic acid-based ointment can be rubbed in at night and washed off in the morning.
Elsewhere: mild steroid creams with an antibacterial and/or antifungal component are usually effective. Alternatives include ketoconazole cream, and sulphur/salicylic acid mixtures. Washing your face daily with an antifungal shampoo containing ketoconazole may also help. Medicated eardrops may help affected ear canals: sometimes a specialist may be needed to clean and pack them.
Occasionally, if the rash is widespread, or not doing well with the treatments listed above, your doctor may suggest a short course of an anti-yeast tablet such as itraconazole.
What can I do?
Once your scalp is clear, go on with an anti-fungal shampoo once a week to stop the rash coming back. If you don’t like the thought of using prescribed antifungal or steroid creams, a plain moisturiser available over the counter, such as aqueous cream, may help to reduce scaling and redness. Changing your diet is not likely to make any difference.
While every effort has been made to ensure that the information given in this leaflet is accurate, not every treatment will be suitable or effective for every person. Your own doctor will be able to advise in greater detail.
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