The effects of an abrasive agent on normal skin and on photoaged skin in comparison with topical tretinoin

Abstract

Two studies were designed to assess the effect of abrasive preparations on the skin and to test the specificity of the effect of topical tretinoin in the management of chronic photodamage to the skin. In the first study two abrasive preparations (Brasivol fine and Brasivol medium) were compared with white soft paraffin and no treatment in eight volunteer subjects for their effects on the epidermis. The study was conducted over 3 days and measurements were taken of the effects on dansyl chloride-induced fluorescence to assess desquamation, epidermal thickness, and the tritiated thymidine autoradiographic labelling index. The abrasives were found to increase the desquamation rate significantly and to increase epidermal thickness and the epidermal labelling index compared to white soft paraffin and no treatment. In the second study the effect of one of the abrasive preparations (Brasivol medium) was compared with 0.05% tretinoin cream (Retin A) on the photodamaged skin of the dorsal aspects of the forearms of 12 subjects over an 8-week period. Cutaneous blood flow measured by the laser-Doppler flowmeter was found to be significantly increased in the abrasive-treated sites, but there was only a non-significant trend to increased blood flow in the tretinoin-treated sites. Measurements of skin thickness using pulsed A-scan ultrasound demonstrated that both treatments produced significant increases in thickness over the 8-week period but the increase was greater for the abrasive treated site. Measurements of the skin extensibility at the treated sites were made using a uniaxial extensometer. Forces needed for 30% skin extension were increased in the abrasive-treated sites only. Measurements of epidermal thickness and of [3H]-thymidine autoradiographic labelling indices showed greater increases in the abrasive-treated sites than in tretinoin-treated sites compared to untreated sites, but these increases were not statistically significant. No significant inflammation and no changes in the degree of elastosis or the presence of a 'repair zone' were found in any of the post-treatment biopsies. The results indicate that some of the changes produced in the skin by topical tretinoin that are taken to indicate a specific antiphotoageing effect may not in fact be specific and can be achieved by an abrasive preparation.