Seborrhoeic Dermatitis

‘Dermatitis’ is a red, itchy, flaky (inflamed) skin complaint; ‘seborrhoeic’ means that the rash affects greasy (sebaceous) skin zones such as the face, scalp, and center of the chest. 

Seborrhoeic dermatitis is widespread and many people don’t even know they have it. Overall it has been reported to affect about 4% of the population, and dandruff (which is mild seborrhoeic dermatitis of the scalp) can affect almost half of all adults.

It can start at any time after puberty and is slightly commoner in men. Babies can also get a short-lived type of seborrhoeic dermatitis in the scalp (cradle cap) and nappy area, which usually clears after a few months.

It is thought that seborrhoeic dermatitis is triggered by an overgrowth of a harmless yeast called Malassezia that lives on the skin, or an overreaction by the skin’s immune system to this yeast. These are not the same as the yeasts that cause thrush or those that are present in foods. 

Seborrhoeic dermatitis is not usually linked to any underlying illness, but it can be stubborn and severe in people with HIV infection, and it is also common in people with Parkinson’s disease. 

Tiredness and stress can sometimes trigger a flare of seborrhoeic dermatitis. It is more common in the cold than in warm weather, and it is not related to diet.

Seborrhoeic dermatitis is managed with treatment that reduces the level of skin yeast – these include creams and shampoo, which can be used safely on a long-term basis. 

Mild steroid creams can be used for short periods to settle any irritation, and the newer non-steroid anti-inflammatory eczema creams (calcineurin inhibitors) are also effective though not licensed for this complaint.

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The symptoms of seborrhoeic dermatitis seem to vary from person to person. Affected areas can be itchy, sore, and sensitive, and flaking skin can be bothersome and embarrassing, especially while wearing dark clothing. Some people have a rash without being troubled.

Affected areas are red with greasy looking skin flakes. It usually affects one or two body areas but can sometimes be widespread. The most ordinary sites are:

• On the scalp: seborrhoeic dermatitis here ranges from mild, flaky skin (dandruff) to a redder, scalier, and sometimes weeping rash. 
• On the face: it often affects the inner eyebrows and creases around the nose and cheeks. The eyelids may also become red, swollen, and flaky (seborrhoeic blepharitis).
• In and around the ears: Some people have inflammation inside, and in the ear cup and behind the ears. The skin can get infected with bacteria, which results in oozing and crusting. 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, 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: affected areas may look lighter (hypopigmented) or darker (hyperpigmented) than surrounding skin.

The diagnosis is made by examining the rash. It is not usually necessary to take a skin sample (biopsy) or to do any blood tests.

If seborrheic dermatitis is severe or unresponsive to treatment, and someone is at risk of HIV, they may get tested. This diagnosis is essential as early treatment of HIV reduces the risk of passing it on and improves the health of the affected person. 

If there is a suspicion of ringworm of the scalp, then skin scrapings can be sent to look for tinea fungus (mycology). 

Seborrhoeic dermatitis can be difficult to distinguish from other kinds of dermatitis when certain areas such as the eyelid or genital area are affected or if it is very widespread.

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

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

Treatment is usually needed on a long-term basis, though sometimes it is possible to take a break. The choice depends on which areas of the body are affected and whether there is much irritation: 

• In the scalp: medicated, anti-dandruff shampoos containing agents such as zinc pyrithione, selenium sulfide, or ketoconazole can be used regularly.
• Elsewhere: anti-yeast creams or ointments are usually effective.
• Washing your body with an antifungal shampoo containing ketoconazole may also help. Leave the shampoo on for ‘5 minutes or so 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 helps lift skin flakes and reduce inflammation.