EEMCO Guidance for the in vivo Assessment of Skin Surface pH

Abstract

The pH of the skin follows a sharp gradient across the stratum corneum (SC), which is suspected to play an important role in controlling the enzymatic activities involved in cellular metabolism and renewal. This gradient is maintained by several systems, such as sweat and sebum secretion and degradation as well as cellular metabolism. At the surface of the skin, what is measured is in fact an apparent skin pH due to extracted material from the SC diffusing into water applied at the surface. pH values recorded at the surface of a semi hydrophobic milieu such as the SC should be interpreted with great caution because it is obvious that hydrogen ions are not in a pure solution at the surface of the skin. For a correct measurement of skin surface pH, it is recommended to follow all practical operating conditions. Care must be taken in identifying the skin site, healthy controls (age, gender, skin type), the time of day of the measurement and the environmental conditions. Also, subjects should receive precise instructions before the test, mainly in terms of hygiene procedure or use of topical products. The interpretation of data should not overlook the fact that even small differences in pH may reflect significant modifications at the molecular level. Although it is usually agreed that the pH of the skin surface may influence the cutaneous microflora, much remains to be learnt about the role of the acid mantle of the skin with regard to defensins and other protective mechanisms.

Vernix Caseosa in Neonatal Adaptation

“…29 Sweat, sebum, topical products, washing, cleansing products, skin site, SC barrier status, pH electrode treatment, site preparation, and meter calibration can all impact skin pH measurements. 30,31 Comparisons of data across studies may reflect inherent variations in test methodology. In this work, skin surface acidification appears to occur earlier in the presence of vernix than under conditions of vernix removal.…”

“…15,16,32 The acid mantle may facilitate colonization of the skin surface with commensal organisms. 30,33 Additional studies are warranted to assess the impact of vernix retention on the process of skin colonization.…”

Chronophysiologie circadienne du cuir chevelu

“…De plus, son amplitude est la plus élevée de toutes nos évaluations. Selon la physiologie complexe du follicule sébacé [31][32][33], ce phénomène ne peut être expliqué que par des modifications temporelles de la rhéologie du sébum à la sortie de l'infundibulum pilosébacé. L'intervention d'un synchroniseur de type température cutanée, elle-même sous l'influence de celle de l'environnement, est concevable.…”

“…La collecte de sébum pendant 45 secondes a été couplée à l'analyse quantitative de la surface relative des gouttelettes lipidiques (%) réalisée par le Visioscan ® (C + K electronic). Toutes les évaluations biométrologiques ont été réali-sées selon les recommandations du groupe EEMCO [27][28][29][30][31], et notamment dans une ambiance contrôlée en température et humidité. …”

Organic cocoa extract -loaded surfactant-based systems intended to skin bioadhesion

“…The maintenance of the correct pH of the skin plays a role in controlling the presence of resident skin microflora as well as supporting important physiological processes like the formation of an optimal structure of the lipid barrier and stratum corneum homeostasis. (Parra, Paye, 2003) All formulations had densities near to density of water (d = 1.0 g/cm³). The cubic phase formulations had a higher density than did the other formulations, and the microemulsion had the lowest density.…”