In vivo measuring of skin softness using the Gas Bearing Electrodynamometer

Synopsis The bio-mechanical properties of the stratum corneum are of great importance for the subjective perception of skin conditions (dry vs. normal), as well as for its multiple functions. The recently developed Gas Bearing Electrodynamometer allows us to measure objectively the viscoelastic properties of the stratum corneum in vivo and to evaluate, in terms of skin softness, the changes of this parameter induced by the application of emollients. The principle of the technique, as designed by Christensen et al., is briefly described in context with our results. During the probe movement, there was a modification of the skin surface relief: compression of the skin furrows ahead of the moving probe, and extension-flattening of the relief behind the probe. The variations of the skin softness were studied in context with the reproducibility of the measurements: the coefficient of variation was found to be about 3%. Considerably higher variations were found as related to: the anisotropy of the skin surface relief, various areas of the body, and individual differences. The effects of emollients and water on the skin softness were studied. Water had a clear effect but of very short duration (around 10 minutes). Water-containing emollients of the type o/w emulsions displayed a distinct long-lasting effect (followed up to 6 hours). Its magnitude was generally higher than that obtained with w/o emulsions. It was found that the emollient's non-volatile components (oil phase) play an important role in the product's softening effect. In conclusion, results to date have established this technique as a promising tool for studying skin softness in general, and effects of topical applications, new formulae and specific ingredients in particular.