Investigation of the homogeneity of the distribution of sunscreen formulations on the human skin: characterization and comparison of two different methods

Abstract

The efficacy of sun protection, mostly realized by the application of sunscreen formulations, is commonly described by the sun protection factor (SPF). Previous investigations have shown that the efficacy of the sun protection inter alia depends on the homogeneity of the distribution of the topically applied sunscreen formulation on the human skin. Therefore, suitable methods are required to determine the homogeneity of topically applied substances on the skin surface. This study provides and compares two different methods, which enable this determination. Laser scanning microscopy allows the analysis of tape strips removed from skin treated with a sunscreen. These reflect the inhomogeneous distribution on the skin that can complementary be determined directly, utilizing a dermatological laser scanning microscope. For the second method, a chromatic confocal setup was utilized, which enables the study of the microtopography of skin replicas before and after the application of a sunscreen product. The two methods were applied for the evaluation of three different sunscreen formulations for each method. A correlation of the homogeneity of distribution with the in vivo SPF could be confirmed. Both methods are suitable to investigate the homogeneity of the tested sunscreen formulations, although they provide different advantages and disadvantages.

Application of optical non-invasive methods in skin physiology

“…These parameters are characterized by the roughness of the skin [8,19], which differ interindividually, reflecting age, lifestyle and genetic aspects. In Fig.…”

In vivovisualization of microneedle conduits in human skin using laser scanning microscopy

“…The system consists of a basic station containing an Argon laser (488 nm), a spectrometer and a control unit [13][14][15]. The basic station is connected to a hand-held device by optical fibers.…”

Die Schattenseiten von Sonne und „gesunder“ Bräuneheiten

“…Neben mimischen und Bewegungsfurchen weist die Haut eine riesige Zahl von Kleinstfurchen auf, in deren Schnittstellen die Haarfollikel liegen. In diesen Furchen sammeln sich die Sonnenschutzmittel -insbesondere die partikulären -während auf den dazwischen liegenden Flächen die Sonnenschutzmittel entweder ungenügend aufgetragen werden oder durch mechanischen Abrieb schneller verloren gehen [13,14,15,16].…”