Seborrhoeic dermatitis

What is seborrhoeic dermatitis

Seborrhoeic dermatitis is a common, harmless, scaling rash affecting the face, scalp and other areas. It is most likely to occur where the skin is oily. The American spelling is ‘seborrheic’, and ‘dermatitis’ is sometimes called ‘eczema’.

Dandruff (also called ‘pityriasis capitis’) is an uninflamed form of seborrhoeic dermatitis. Dandruff presents as scaly patches scattered within hair-bearing areas of the scalp.

What does seborrhoeic dermatitis look like?

Within the scalp, seborrhoeic dermatitis causes ill-defined dry pink or skin coloured patches with yellowish or white bran-like scale. It may spread to affect the entire scalp.

Seborrhoeic dermatitis is common within the eyebrows, on the edges of the eyelids (blepharitis), inside and behind the ears and in the creases beside the nose. It can result in pale pink round or ring shaped patches on the hairline.

Sometimes it affects the skin-folds of the armpits and groin, the middle of the chest or upper back. It causes salmon-pink flat patches with a loose bran-like scale, sometimes in a ring shape (annular). It may or may not be itchy and can be quite variable from day to day.

What is the cause of seborrhoeic dermatitis?

Seborrhoeic dermatitis is believed to be an inflammatory reaction related to a proliferation of a normal skin inhabitant, a yeast called Malassezia. The main species found in the scalp is M. globosa. It produces toxic substances that irritate the skin. Patients with seborrhoeic dermatitis appear to have a reduced resistance to the yeast.

Infantile seborrhoeic dermatitis

It is uncertain whether infantile seborrhoeic dermatitis is the same condition. This arises in newborn babies up to the age of six months. It usually presents as cradle cap, but infantile seborrhoeic dermatitis may also affect skin creases such as armpits and groin (when it presents as a type of napkin dermatitis). Non-itchy salmon pink flaky patches may appear on the face, trunk and

Treatment

Seborrhoeic dermatitis in adults may be very persistent. However, it can generally be kept under control with regular use of antifungal agents and intermittent applications of topical steroids.

Infantile seborrhoeic dermatitis usually clears up completely before the baby is six months old and rarely persists after one year. If treatment is required, mild emollients, hydrocortisone cream and / or topical ketoconazole are useful.