It is a red, itchy, flaky rash that affects greasy skin areas in the face, scalp and center of the chest.

It is very common and affects about 40 % of the population, and dandruff (which is mild seborrheic dermatitis of the scalp) can affect almost half of all adults. It starts after puberty and is commoner in men. Babies can also get a short lived type of seborrheic dermatitis in the scalp (cradle cap), which clears after a few months.

What causes it?

It is thought that it is triggered by a yeast called Malassezia that lives on the skin, or an over-reaction by the skin’s immune system to this yeast.

It is more common in cold than in warm weather, and it is not related to diet.

Symptoms:

Affected areas are red with greasy skin flakes. They can be itchy, sore and sensitive and flaking skin can be embarrassing, especially with dark clothing.

The commonest sites are:

On the scalp: ranges from mild dandruff to a red, scaly weeping rash.

On the face: it affects the eyebrows and creases around the nose and cheeks. The eyelids may also become red, swollen and flaky.

Ears: inside the ear canals, in the cup of the ear and behind the ears. Inflammation in the ear canal can cause it to become blocked.

On the front of the chest and between the shoulder blades: well-defined, round pink-red patches with mild scaling.

In the skin folds: it often affects moist areas such as the skin under the breasts, in the groin, under the arms, or in folds of skin on the abdomen. The skin is pink and shiny with surface cracks.

In darker skin: may look lighter or darker than the surrounding skin.

Severe scalp seborrheic dermatitis can resemble psoriasis. In psoriasis, the scales are thicker and whiter and the face is not usually affected

How is it treated?

Seborrheic dermatitis is managed with treatment that reduces the level of skin yeast ,such as creams and shampoos, which can be used safely on a long time. Mild cortisone creams can be used for short periods for any irritation.

Treatment

Treatment can improve and sometimes clear seborrheic dermatitis, but there is no permanent cure and the complaint tends to come back when treatment is stopped.

Treatment depends on the areas affected and degree of irritation:

In the scalp: anti-dandruff shampoos containing agents such as zinc pyrithione, selenium sulphide or ketoconazole can be used regularly. For best results, apply into the scalp, then wait 10 minutes before washing. Thick scales can be removed before shampooing by applying a descaling preparation containing salicylic acid.

On the body: anti-yeast creams are usually effective and can be used safely as long-term treatment. Examples include clotrimazole, miconazole and nystatin. They are sometimes combined with a mild cortisone for a few weeks to control inflammation. Washing the body with an antifungal shampoo containing ketoconazole may also help. Leave the shampoo on for 5 to 10 minutes before rinsing it off. In the ear canals: medicated eardrops may help. Do not clean the ears with cotton buds as this causes more irritation.

On the eyelids: carefully cleaning between the lashes with an eyelid cleanser or baby (non-sting) shampoo which helps to lift skin flakes and reduce inflammation.

Occasionally, if the rash is widespread or resistant to the treatments listed above, the doctor may suggest an oral anti-yeast medication.

Once your scalp is clear, continue using an antifungal shampoo once a week to reduce the chance of coming back. Changing diet is not likely to make difference.