In vitro standard methods are available and accepted worldwide to assess UVA protection of sunscreen products. Though, harmonisation of methods has made progress in the last decade, still two differing methods - one by FDA the other by ISO - are in use. In a multicentre study including 9 centres in Germany, 4 different commercial sunscreen products were assessed using both methods to discover their similarities and differences. UVA protection factor and Critical Wavelength were detected at various substrate type (sandblasted versus moulded PMMA plates), at different surface roughness of the plates as well as at different product application dose using two different irradiation spectra. Results: The strongest influence on UVA protection factor results from the surface roughness of the plates. Depending on the roughness (accepted range of 2 to 7 gm in the FDA method) a variability in the UVA protection factor of up to 25% was observed, while the much narrower definition of plate roughness by ISO (4.5 to 5.2 mu m) had no relevant influence on the test results. Sandblasted plates in our assessment led to higher UVA protection factors and produced less scattered results compared to moulded plates. These differences were not pronounced. Application dose and spectra of the irradiation source were of negligible influence on UVA protection factor results for the investigated UV-filter combinations. The UVA protection factor which is the endpoint of the ISO method was found to be a parameter with a high potential to differentiate among different test products. The endpoint of the FDA method - the Critical Wavelength - was found to be an unambitious endpoint. Insensitivity to all described modifications of the method was observed. All investigated products performed similar and passed the Critical Wavelength criteria independent of method and parameters.

Modern sunscreens are well suited to provide sufficient protection in the UV range because the filter substances absorb or scatter UV radiation. Although up to 50% of radicals are formed in the visible and infrared spectral range during solar radiation protection strategies are not provided in this range. Previous investigations of commercially available products have shown that in addition to physical filters, antioxidants (AO) are necessary to provide protective effects in the infrared range by neutralizing already formed radicals. In this study, the efficacy of filter substances and AO to reduce radical formation in both spectral ranges was investigated after UV/VIS or IR irradiation. Optical properties and radical protection were determined for the investigated creams. It was found that organic UV filters lower radical formation in the UV/VIS range to 35% compared to untreated skin, independent of the presence of AO. Further reduction to 14% was reached by addition of 2% physical filters, whereas physical filters alone were ineffective in the UV/VIS range due to the low concentration. In contrast, this filter type reduced radical formation in the IR range significantly to 65%; similar effects were aroused after application of AO. Sunscreens which contain organic UV filters, physical filters and AO ensure protection in the complete solar spectrum.

Correspondence: Nicole Gerlach DermaTronnier, Alfred Herrhausen-Str 44, 58455, Witten, Germany Email nicole.gerlach@uni-wh.de Abstract: The aim of this study was to assess the effect of 2% bis-ethylhexyl hydroxydimethoxy benzylmalonate (HDBM; RonaCare AP) as an active ingredient in the treatment of oily and blemished skin. This study was carried out as a randomized, placebo-controlled, single-blind study on 44 test subjects with blemished skin over a period of 8 weeks. Sebum measurement, skin inflammation/redness scoring by an expert, photographic documentation and a self-assessment with regard to skin improvement, and tests of skin compatibility and galenic characteristics were performed. Treatment with 2% HDBM resulted in a significant reduction of sebum excretion and showed efficacy against inflamed/red lesions also shown by photographic documentation. Efficacy and galenic performance of 2% HDBM were judged to be superior to the placebo emulsion. Additionally, 2% HDBM was well tolerated; approximately 80% of the test subjects rated the compatibility as good to very good.

In the past, several attempts have been made to develop in vitro methods for determining protection against UV radiation. To date however, there is no broadly accepted method. Various known and unknown parameters influence the transmission measurements of scattering films, such as the multifaceted compositions of sunscreens, the technical limitations of measurement devices as well as the difficulty to apply very thin films of sunscreen in a reproducible manner throughout different laboratories. In vitro data were measured in this multicenter study to compare possible methodologies and strategies for an in vitro approach to the sun protection factor (SPF). This publication will not present a final in vitro SPF test method, but it will point out which technical side effects may influence such a method. Influential factors such as the quality of spectrophotometer used, the amount of product applied, pretreatment of samples, time and temperature of equilibration, size of the measured surface, the application process or the calculation on the basis of standardized data are presented and discussed. Finally, a reduction of the standard deviations within single laboratories could be realized for in vitro SPF testing, but no improvement of the interlaboratory comparison was obtained. The development of a valid and reliable SPF in vitro test still remains a challenge, and further work is necessary to develop a satisfactory method.

Ideally, anti‐(photo)ageing concepts should provide maximum efficacy, perfect stability and cosmetic (formulation) elegance. The need for high efficacy paired with excellent stability appeared contradictive but was resolved by designing complete redox systems rather than antioxidants alone. We here introduce a new class of cosmetic redox pairs, each comprising the initial antioxidant plus its oxidation product. The chemical properties of the oxidation product are the key to enabling the system to maintain or even increase its initial efficacy. A series of antioxidant tests were used to carefully characterize single redox pair components for comparison with traditional antioxidants such as vitamin C and E derivatives (DPPH, lipid and TEAC assays). Kinetic studies on the photobehaviour of a selected redox pair were carried out in cosmetic emulsions with solar simulation and monitored by UV spectroscopy and high performance liquid chromatography. Hydroxy dimethoxybenzyl malonate (HDBM) is a pure transparent cosmetic oil. It shows excellent cosmetic stability coupled with extraordinary antioxidant properties. This controlled activity can be explained well by the presence of its oxidation product hydroxy dimethoxybenzylidene malonate (HDBMox), which provides ongoing antioxidant activity plus excellent UVA absorbing properties. The redox pair described here provides the advanced on‐demand benefit of a non‐UV‐absorbing photoprotector that is converted into its UV‐absorbing equivalent upon light exposure.

It is often debated that the protection against solar-induced erythema under real conditions is dependent upon the amount of sunscreen applied. It is believed that when too little is applied a lower sun protection than indicated on the label will result. The aim of this study was to quantify this effect. In this multicenter study, the influence of three different amounts (0.5, 1.0, 2.0 mg/cm2) of three commercial sunscreen products in three reliable test centers was investigated according to the test protocol of The International Sun Protection Factor Test Method. The main result was a linear dependence of the SPF on the quantity applied. Taking into consideration the volunteer-specific variations, an exponential dependence of confidence interval of the in vivo SPF and amount applied was found. The highest amount applied (2.0 mg/cm2) was linked to the lowest confidence intervals. Thus, from the point of view of producing reliable and reproducible in vivo results under laboratory conditions, the recommendation of this multicenter study is an application quantity of 2.0 mg/cm2.

The influence of the synergy effects between organic and inorganic UV filter substances on the sun protection factor (SPF) of topically applied sunscreen formulations is investigated. The medium is considered to have reflection, absorption, and scattering properties. The distribution of photons in this medium is investigated by Monte Carlo calculation. Typical optical parameters of the skin and substances are used to characterize the synergy effect. The results of the model calculation are checked by in vitro and in vivo measurements investigating the influence of different types of scattering microparticles on the absorption efficacy of topically applied formulations. It is found that the inorganic filter substances act as scattering microparticles in the upper skin layers. They increase the optical pathway of the photons in the topically applied absorbing formulation also localized there. In this way, more photons are absorbed, increasing the SPF. The results obtained are important for the optimization of the SPF of sunscreen formulation containing organic and inorganic UV-filter components.

Today micronised titanium dioxide is widely used in cosmetic sunscreen emulsions due to its broad UV-absorption spectrum and its high aesthetical acceptance. In addition to its UV-absorption capacity, titanium dioxide can also be used as a stabilizing agent for pickering-emulsions [J. Chem. Soc. Trans. 91 (2001) 1907]. In the present work studies were performed in order to determine the effect of different surface modified titanium dioxides on the type and the stability of surfactant-free emulsions. The investigated emulsions contain nanometer-sized titanium dioxide particles, medium chain triglycerides and water as their main components.Present results indicate that stable pickering-emulsions can be formed using nanometer-sized titanium dioxides. The type and stability of the prepared emulsions depend on the wettability of the stabilizing TiO2 nanoparticles. Particle wettability is influenced by the type, the amount, and the combination of the used inorganic and organic materials used for the surface modification of TiO2. (C) 2003 Elsevier B.V. All rights reserved.

The effectiveness of sunscreens was originally achieved by incorporation of soluble organic UV absorbers such as cinnamates and others into cosmetic formulations. Determinations of the sun protection factor (SPF) of emulsions containing different organic UV absorbers clearly indicate that the efficacy depends on the absorption characteristics of each single UV filter substance. Nowadays, micronised pigments such as titanium dioxide or zinc oxide have also been found to be protective against harmful UV rays. Our investigations using optical and electron microscopy proved that neither surface characteristics, particle size nor shape of the micronised pigments result in any dermal absorption of this substance. Micronised titanium dioxide is solely deposited on the outermost surface of the stratum corneum and cannot be detected in deeper stratum corneum layers, the human epidermis and dermis.

Hoppe U., Lübeck, Germany Jacobi Ute, Martinsried, Germany Kalia Y.N., Archamps, France Kemeny Lajos, Szeged, Hungary Koch Stefan, Bad Saarow-PIeskow, Germany Korting Hans-Christian, München, Germany Kragballe Knut, Aarhus, Denmark Krakhecke A.G., Mato Grosso do Sul, Brazil Kramer Axel, Greifswald-Eldena, Germany Mahrle G., Köln, Germany Maibach Howard I., San Francisco, Calif., USA May Ekkehard, Berlin, Germany Meffert Hans, Berlin, Germany Messenger A., Sheffield, United Kingdom Middelkamp Maritza, Amsterdam, The Netherlands Mukhtar Hasan, Madison, Wisc., USA Neubert Reinhard H.H., Halle, Germany Nohynek Gerhard, Asnieres, France Pardon M.C., Paris, France Parra Juez José Luis, Barcelona, Spain Philips Neena, Heverlee, Belgium Potapenko A.Y., Moscow, Russia Rogiers Vera, Brussels, Belgium Rudolph Thomas, Darmstadt, Germany Ahmad Nihal, Madison, Wisc., USA Ahsan Haseeb, Madison, Wisc., USA Altmeyer Peter, Bochum, Germany Andersen Klaus, Odense, Denmark Astner Susanne, Berlin, Germany Baron J.M., Aachen, Germany Benfeldt Eva, Hellerup, Denmark Bernard Bruno A., Clichy, France Bimczok Rudolf, Darmstadt, Germany Bito T., Berkeley, Calif., USA Blume-Peytavi Ulrike, Berlin, Germany Böhm Markus, Münster, Germany Borges C.R., Salt Lake City, Utah, USA Butz T., Leipzig, Germany Coffey G.P., South San Francisco, Calif., USA De Paepe Kristien, Brussels, Belgium Eady Anne E., Leeds, United Kingdom Elsner Peter, Jena, Germany Fluhr Joachim, Jena, Germany Gers-Barlag Heiner, Hamburg, Germany Ghannoum M.A., Cleveland, Ohio, USA Gollnick Harald M., Magdeburg, Germany Hadgraft Jonathan J., Chatham in Maritime, United Kingdom Heinrich Ulrike, Witten, Germany Herzog Bernd, Grenzach-Wyhlen, Germany Hipler Uta-Christina, Jena, Germany

Electron microscopy visualisation and light microscopic investigations of three different application forms of titanium dioxide proved that neither surface characteristics, particle size nor shape of the micronised titanium dioxide result in any dermal absorption of this substance: Micronised titanium dioxide is solely deposited on the outermost surface of the stratum corneum and cannot be detected in deeper stratum corneum layers, the human epidermis and dermis.

In order to help clarify the controversially discussed dermal uptake properties of micronized titanium dioxide (TiO ), we conducted extensive in vitro dermal absorption studies with ’Franz‐type’ diffusion cells on excised porcine skin. After biopsies and chemical fixation, the overall localization of TiO in the skin was analyzed by means of transmission electron microscopy (TEM). The lateral and vertical distribution of TiO within the stratum corneum (SC) was investigated by tape stripping and subsequent scanning electron microscopy (SEM) in combination with energy dispersive X‐ray analysis (EDXA).TiO was found exclusively on the outermost SC layer. The surface deposit, as displayed by TEM, featured clearly distinguishable agglomerates as well as single particles with a characteristic cubic shape and a primary particle size of about 20–50 nm. Concurrently, SEM/EDXA micrographs first showed an even distribution of TiO on the skin surface. After 10‐fold stripping, however, TiO was found to be localized only in the furrows and not on the partially removed ridges of the skin surface. SEM/EDXA micrographs of the adhesive tape strips revealed a characteristic pattern of stripped material and free regions. This pattern was an imprint of the skin’s topography. Hence, tape stripping initially removed TiO and SC layers only from the ridges and not from the deeper furrows. Continued stripping increasingly yielded material from the deeper contours of the SC surface. TiO was found only in traces in the upper part of the follicle without any evidence of uptake into the follicular epithelium. This indicates that there is not any relevant penetration via the follicular route.We conclude that due to the microtopography of the skin, the strip number normally does not reflect the SC layer number. Accordingly, tape stripping results should always be interpreted with care, especially in the case of topically applied particles, as even higher numbers of subsequent strips may still sample material from the outermost SC layer of the deeper furrows, which could be interpreted falsely as penetrated material. Our results clearly demonstrate that TiO homogeneously and completely covers the outermost SC layer. It is neither delivered to the SC nor to the underlying skin layers when applied topically to porcine skin in vitro in the cosmetic vehicle used here. These findings underscore the safety of this micronized inorganic UV filter.