Seborrhoea is not a feature of seborrhoeic dermatitis.

The sebum excretion rate from forehead skin was measured in 44 patients with classic seborrhoeic dermatitis and 200 control subjects. The mean excretion rate was normal in the 29 men with seborrhoeic dermatitis and significantly reduced in the 15 women with the disease. This study showed that seborrhoeic dermatitis is not usually associated with seborrhoea, and therefore "dermatitis of the sebaceous areas" may be a more accurate term.