Identification of Skin Sensitivity through Corneocytes Measurements.

Abstract

Surveys conducted in many nations suggest that up to 50% of cosmetic users believe they have sensitive skin and products specifically designed for this skin type have become an important cosmetic category. In developing such products, objective assessment of the degree and type of sensitivity is desirable. Unfortunately, currently available methods, including measurements of trans-epidermal water loss (TEWL) and lactic acid stinging tests, do not correlate well with self-assessed sensitivity and cannot be used to identify persons who are more prone to develop adverse skin reactions than other users. A simple, more reliable non-invasive method for detecting skin sensitivity is needed. In developing such a method, it is necessary to understand the exact meaning of “sensitivity” as used by consumers to describe their skin condition. Our extensive surveys of 130 subjects, conducted over a one-year period and taking into consideration seasonal variations, revealed that the meaning varies somewhat among individuals, but that there is a consensus on specific skin conditions to which they refer when they report having sensitive skin, These conditions include tendencies for their skin to itch, develop redness and become dry and flaky. Our investigations revealed that the development of skin sensitivity is often related to a reduction in the barrier function of the stratum corneum, and thus a method could be developed using certain biophysical properties of corneocytes to predict skin sensitivity. Our search for such an objectively measurable sensitivity index led us to the discovery that a certain parameter of the average projected area of corneocytes obtained via tape stripping at a specific area of facial skin can be used for this purpose. Our new method, called APAc, is more reliable and convenient in predicting self-assessed skin sensitivity than are TEWL or lactic acid stinging tests.