How to diagnose seborrhoea?

The diagnosis of seborrheic dermatitis is usually made on clinical grounds, based on a history of waxing and waning severity and by the distribution of involvement upon examination.

A skin biopsy may be needed in persons with exfoliative erythroderma, and a fungal culture can be used to rule out tinea capitis, though tinea capitis is rare in adults. Dermatopathologic findings of seborrheic dermatitis are nonspecific and typically include the following:

• Hyperkeratosis
• Acanthosis
• Accentuated rete ridges
• Focal spongiosis
• Parakeratosis                                                                                                                                                                                                                                                                                             - Psoriasis is distinguished by regular acanthosis, thinned rete ridges, exocytosis, parakeratosis, and an absence of spongiosis. Neutrophils may be seen in both diseases.