Skin colour typology and suntanning pathways

Abstract

Synopsis The evaluation of sun-product efficacy, with laboratory solar simulators or in actual sun, implicates clinical and subjective assessment of the various skin responses in terms of wavelengths constitutive of solar light. These photobiological responses vary according to skin types and particularly to basic skin melanic content, i.e. with skin colour. Now, the instrumental measurement of live skin colour has become easier to perform, fast and reliable. Based on the standard CIE-L*a*b* colour system and correlated with the human eye, this technique was used to define the skin colour domain of the caucasian population, to propose a skin colour classification, and then to objectively follow, over a three week period, the dynamics and kinetics of tanning induced by UVB, UVA and UVB +/- A multi-exposures on the three skin categories. The specific directions in the three-dimensional L*a*b* colour space of the tanning components, i.e. erythema, immediate pigmentation and constitutional melanization, as well as the resulting tanning pathways, were analysed and defined in the three-dimensional colour space, using a vectorial method. The UVB, UVA and UVB +/- A tannings were differentiated by their intensity, their hue and especially their lasting capacity: UVA tanning clearly appeared more lasting than UVB. In addition, the UVA*UVB interaction on tanning intensity was not found to be significant. With the skin colour classification and the tanning models, this comprehensive study supplies a basic tool for the colorimetric interpretation of the skin phenomena involved, provided that this interpretation is always considered in the three dimensions of the colour space. It also suggests some useful practical applications for sun product formulation and evaluation.

Variations in skin colour and the biological consequences of ultraviolet radiation exposure

“…For this reason, another classification system has been proposed based on the colorimetric parameters L* (luminance) and b* (yellow/blue component) and determination of the individual typology angle (ITA). 20 Using this classification system allows skin colour types to be classified into six groups, from very light to dark skin. The validity of the ITA has been evaluated with regard to its correlation with constitutive pigmentation using Fontana-Masson staining, which highlighted the differences in melanin content and distribution between distinct groups.…”

“…This allowed skin colour types to be classified into six groups, from very light to dark skin: very light > 55°> light > 41°> intermediate > 28°> tan >10°> brown > À30°> dark 20 ( Fig. 1).…”

The benefit of daily photoprotection

“…The specific directions in the 3-dimensional L*, a*, and b* color space of the tanning components, ie, erythema, immediate pigmentation, and constitutional melanization, and the resulting tanning pathways, may be analyzed and defined in the 3-dimensional color space using a vectorial method. 13 Individual . For all these parameters, the results were expressed as the variation between day 43 and day 1.…”

EEMCO Guidance for the in vivo Assessment of Skin Greasiness

“…This shifts the natural 'white' colour of the tape to a colour closer to that of the skin itself [54]. Reflectance colorimetry is conveniently expressed as DE*ab or calculated following the variation in the so-called individual typology angle (TTA°) [55,56]. The benefit of such an approach is the ability to obtain multiple measurements without removing the tape and therefore to learn the kinetics of sebum output.…”