Seborrhoeic Dermatitis

Diagnostic feature :

Seborrhoeic dermatitis is characterized by a distinctive morphology (red, sharply marginated lesions covered with greasy looking scales) and a distinctive distribution (scalp, face and upper trunk) which are areas rich in sebaceous glands.

Clinical patterns :

Adult (may be associated with Parkinsonism and HIV infection)

Scalp Dandruff is usually the earliest manifestation. In chronic cases, there may be hair loss which is reversible when the inflammation is controlled. Ears are a common site of involvement.

Face Medial sides of the eyebrows, glabella, nasolabial fold, are predilected sites. Blepharitis is a feature.

Trunk Petaloid form is commoner than the pityriasiform. Follicular papules with greasy scale that may become confluent, and commonly found over the sternum and interscapular region.

Infantile

The eruptions in infants frequently first appear between the third and eighth weeks of life. It may start in the napkin area, the face and scalp, and occasionally on the trunk outside the napkin area. The rash comprises well-defined areas of erythema and scaling with tiny vesicles. Papular and lichenified lesions are not seen. Typically the infant is well and not irritable (c/w atopic dermatitis). The prognosis is usually good. Most uncomplicated cases clear in 3 to 4 weeks.

Differential diagnoses :

Psoriasis, pityriasis rosea, pityriasis versicolor, drug eruption and lichen simplex in adult. Intertrigo, irritant contact dermatitis, atopic dermatitis, psoriasis and eczematous eruptions in immunodeficiency disorders in infants.

Management :

Adults

Ketoconazole shampoo is very effective in removing dandruff. Shampoos that contain salicylic acid, selenium sulphide, zinc pyrithione and tar are alternatives. For thick scalp scale and crust, sulphur salicylic emulsion can be applied before bed and shampooed next morning. Steroid lotion applied twice daily provides symptomatic relief but may relapse.

Lesions on face, chest can be treated by weak topical steroid and antiseborrhoeic shampoo. Washing the affected areas with soap can be a useful adjunct. 2% Ketoconazole cream once a day is highly effective in difficult cases.

Scaling of blepharitis may be suppressed by frequent washing with zinc or tar containing antidandruff shampoos. Prolonged use of steroid lotion on the eyelids causes glaucoma and should be avoided. 2% ketoconazole cream once a day should be tried in resistant cases.

Infants

Cradle cap should be oiled regularly with warm olive oil and washed off few hours later with 5% cetrimide shampoo. Erythema and scaling on the body can be treated with weak topical corticosteroid cream topical antibiotic if infection is present. Shampoo that contains salicylic acid or selenium sulphide should be avoided in neonates for the risk of systemic absorption.