There is evidence in some individuals that seborrhoeic dermatitis is an immuno-allergic reaction induced by nicotine as hapten. Nicotine is present in passive smoking, botanic areas, some foods at very low levels, smokeless tobacco and chewing gums. The successful use of topical ketoconazole as an anti-fungal treatment has been recently explained by its anti-leukotrienes properties in vitro, in vivo and by its capacity to inhibit the leukotrienes-mediated anaphylactic bronchoconstriction in the guinea-pigs. The occurrence of hypersensitivity to nicotine in seborrhoeic dermatitis remains to be determined, but an other original view is open for a better comprehension of an old disease.