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.

A novel approach to the search for in vitro alternatives to in vivo eye irritancy testing.

Cytotoxicity in terms of haemolytic potency in vitro of eight surfactants failed to correlate with in vivo rabbit eye irritancy. Ability of the same surfactants to block spontaneous contractions of mouse and rabbit isolated ileum (especially the latter), correlated better with in vivo findings in rabbit eyes. Effectiveness in blocking ileum contractions may depend both on ability to penetrate this tissue and to act at the target site.

The effect of dose and vehicle on early tissue damage and regenerative activity after chloroform administration to mice.

The relationship between the acute toxicity of orally-administered chloroform and its long-term tumorigenic potential was studied in male mice of the CFLP outbred Swiss albino mouse strain. A single dose of approximately 18 mg CHCl3/kg had no detectable acute toxic effect on the liver or kidneys and did not stimulate regenerative activity, whereas both toxicity and subsequent tissue regeneration were observed with single doses of about 60 mg/kg or higher. The severity of the toxic effects and regenerative changes was greater when corn oil was used as a vehicle for chloroform than when the vehicle was a toothpaste base.

Bacterial mutagenicity studies on chloroform in vitro.

Chloroform was tested for mutagenicity in the Salmonella/microsome assay using five strains of Salmonella typhimurium. In view of previous reports describing the development of liver and kidney tumours in some experiments involving long-term administration of chloroform to rats and mice, the mutagenicity tests were carried out in the absence of any S-9 microsomal-enzyme preparation and in the presence of S-9 microsomal-enzyme preparations derived from (a) livers and (b) kidneys of rats and mice previously exposed to the microsomal-enzyme inducer Aroclor 1254. No evidence of potential mutagenicity was observed under any of the test conditions.

The effect of hair care products on dandruff.

Synopsis Although the role of micro-organisms located on the surface of the scalp is disputed by some authors, lipolytic organisms within the hair follicle may still be implicated in the causation of dandruff. Scale formation appears to be an adaptive response to threshold scalp irritation, taking the form of minimal parakeratosis possibly induced by products of lipolysis permeating thin regions of the horny layer. No single pathogen is yet clearly identifiable but effective anti-dandruff compounds display good antimicrobial activity against the typical lipolytic scalp microflora; this activity is retained in the presence of sebum and a feature of the most efficacious anti-dandruff agents is their good substantivity to the epidermal horny layer.