Using a hypomitotic agent, triamcinolone acetonide, and a hypermitotic agent, retinyl propionate, we investigated the relationship between epidermal mitotic activity and stratum corneum renewal time of topically treated skin as determined by the dansyl chloride staining technique. Treatment with the base cream resulted in a reduction in renewal time compared with an untreated control site. The predicted increase in renewal time with the hypomitotic agent and reduction with the hypermitotic agent was only observed when daily treatment was commenced 2 weeks prior to and continued after dansyl chloride staining and not when treatment was started after staining. These results indicate that in order to use cell renewal methods to demonstrate changes in mitotic activity brought about by topical treatments, it is necessary to pre-treat the skin with the test material to establish full epidermal equilibrium at the changed mitotic state before labelling with dansyl chloride. Meaningful claims for effects on cell renewal of specific cosmetic ingredients should only be made after comparison with a base cream treated site, both having been allowed to equilibrate, rather than on the basis of comparison with untreated skin.

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