Squamometry: a tool to move from exaggerated to more and more realistic application conditions for comparing the skin compatibility of surfactant-based products.
Squamometry consists of sampling the most superficial layers of the stratum corneum by means of a sticky tape firmly pressed onto the skin. Harvested cells are stained and the intensity of staining is related to the level of skin surface alterations caused by surfactant-based products. This method is extremely sensitive and the current study demonstrates that, thanks to squamometry, product mildness can now be compared without causing skin irritation due to exaggerated application conditions. In a 15 minute patch test, squamometry assessments ranked a series of surfactants as expected from their known irritation potential, without causing clinical signs of irritation. Similarly, the counter-irritant effect of amphoteric and nonionic surfactants on the irritation potential of anionic surfactants was evidenced. In a 30 minute patch test, shampoos were ranked by squamometry as they were in a classical Soap Chamber Test (48 hours of application). Finally, four hand dishwashing liquids were tested for one week by consumers according to a procedure similar to normal usage of the products, and were classified by squamometry as they were in a previous Soap Chamber Test. In conclusion, this study suggests that squamometry is able to predict the skin compatibility of surfactant-based products even after very short and realistic application times to volunteers' skin. Providing further validation, this technique could allow a move to test conditions much closer to the normal usage procedure of the products, to design test protocols much more respectful of panelists' skin condition, and to get information on product tolerance very quickly.
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Colgate-Palmolive R&D, Avenue du Parc Industriel, 4041 Milmort, Belgium.
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