Seborrhoeic Dermatitis

It is also known as seborrhoeic eczema. The usual age of onset is at puberty. An infantile form exists but it will not be considered here.

Seborrhoeic dermatitis is believed to be an inflammatory reaction to a yeast called Malassezia but formerly known as Pityrosporum ovale. This is a normal skin commensal. Patients with seborrhoeic dermatitis appear to have a reduced resistance to the yeast.

The disease is not contagious or related to diet, but it may be aggravated by illness, psychological stress, fatigue, change of season and reduced general health. Immunodeficiency, especially HIV infection and neurological disorders such as Parkinson's disease and stroke predispose to it.¹

In adults it tends to affect people with greasy skin. It causes scaling around the nasolabial fold, over the bridge of the nose, in the eyelashes and eyebrows, and in front, behind or in the ear.² Usually there is an associated fine scaling in the scalp to produce dandruff and there may be plaques of fine scaling over the sternum³ and between the shoulder blades.

On the scalp, there may be ill-defined dry pink patches with yellowish or white bran-like scale. It may affect the entire scalp.

It often affects the eyebrows and, on the edges of the eyelids can cause blepharitis.

Less commonly, seborrhoeic eczema can be associated with ill-defined erythematous patches, papules or plaques in the flexures. This means axilla, groin and under breasts. Another variant is called pityrosporum folliculitis and is due to overgrowth of the yeast. Fine follicular papules and some pustules involve much of the trunk and back.

The distribution is usually characteristic, and the association of fine dandruff is required for a firm diagnosis. Rosacea on the face is not scaly, spares the nasolabial fold, and consists of papules and pustules on an erythematous base situated on cheeks, chin, tip of nose and forehead.

The basis of treatment is antifungal medication with intermittent topical steroids.⁴

Scalp

• Medicated shampoos may contain ketoconazole, selenium sulfide, zinc pyrithione, coal tar or salicylic acid. An antifungal agent is particularly useful. They are used twice a week for at least a month after which the frequency may be reduced but it is a chronic disease that will require long term management.⁴
• Pruritis of the scalp is a problem that may be eased by steroid scalp applications. Intermittent use for a few consecutive days may be helpful.
• Coal tar cream can be applied to scaling areas for several hours and then removed by shampooing.

Steroid creams should be used for short courses only for fear of rebound effect and "dependence".

Face, Ears, Chest and Back

• Keep the skin clean but avoid soap.
• Ketoconazole or another antifungal cream may be used once daily for 2 to 4 weeks. This can be repeated as necessary.
• 1% Hydrocortisone cream can be applied once or twice daily for a week or two. Again, intermittent courses may be required for this chronic condition.
• Severe cases may benefit from ultraviolet light.

There may be occassions when topical antifungal creams do not seem to eradicate the infection. Under these circumstances, 10 days of oral itraconazole may achieve the desired result.

A severe, explosive onset of seborrhoeic dermatitis may suggest HIV infection, regardless of age. It may appear as a butterfly rash on the face and resemble the acute eruption of systemic lupus erythematosus. The dermatitis appears early with AIDS, affects 25-50% of those with the condition and is more extensive and more active with diminished T-cell function. Topical preparations may suffice, but if severe, treatment with 400 mg of oral ketoconazole daily for 2 weeks may be necessary.¹

The condition usually responds well to treatment but often relapses and maintenance or intermittent treatment is required.

Usually this should be managed in primary care. Difficulty in diagnosis or effective management may require referral.