Dandruff: infection or not?

Synopsis The presence of apparently normal corneocytes as well as parakeratotic material in dandruff scales suggests that atypical keratinization in the scalp epidermis has not been of long duration. Abundance of hair fat on the scalp after puberty, colonization by fat-splitting micro-organisms (notably yeasts of the genus Pityrosporum) and transitory upsurges of epidermal mitosis in response to fatty acids produced by lipolysis of sebum triglycerides within the hair follicles, especially those in the anagen phase, seem likely to be implicated in the generation of dandruff scaling. Antidandruff efficacy apparently calls not only for antifungal potency demonstrable in vitro but also for the ability, when incorporated in a suitable formulation, to reach the microflora within the hair follicles and to inhibit the metabolic activity of these microorganisms even in the presence of sebum. The in vivo demonstration of an alleged 'anti-hyperproliferative'effect of an antidandruff compound has been described but probably has only coincidental relationship to its normal function in the control of dandruff, which seems more likely to depend on its antimicrobial properties. The available evidence thus tends to favour the view that the scalp microflora have a predominant role in the generation of dandruff. Pellicules: origine microbienne ou non microbienne?