HDRS - Hybrid Diffuse Reflectance Spectroscopy: Non-Erythemal In Vivo Driven SPF and UVA-PF Testing.

BACKGROUND/AIMS: In order to define a label SPF of topically applied sunscreens, in vivo test methods like ISO 24444, FDA Guideline, and the Australian Standard are used worldwide. The basis of all these methods is to induce an erythemal skin reaction by UV irradiation to find the level of MEDu and MEDp (Minimal Erythmal Dose unprotected and protected). In vitro methods replacing the human skin by any kind of nonhuman material are still not available. Thus, offering the new hybrid diffuse reflectance spectroscopy (HDRS) technique that can maintain an in vivo level for SPF testing while neglecting the UV-dose-related erythemal skin reaction is a perfect combination to take care of sun protection and any ethical concerns in SPF testing nowadays. METHODS: HDRS is a combination of in vivo diffuse reflectance spectroscopy measurements on the skin and in vitro transmission measurements of a sunscreen on a roughened polymethylmethacrylate plate. By this technique, the in vivo behavior of the investigated sunscreen on the skin is measured as well as the UVB absorption, which is still nonvisible in the reflectance technique. In order to establish an alternative method for in vivo SPF and UVA-PF testing, a huge number of sunscreens (250 samples) were measured by HDRS and compared with the worldwide accepted standards ISO 24444, ISO 24442, and ISO 24443. The variety of sunscreens measured reflect a wide range of different types of formulations as well as a wide range of SPFs (5-120) to validate this new alternative SPF testing procedure. RESULTS: Far-reaching statistical data analyses show an excellent link between the new nonerythemal-driven HDRS-SPF technique and ISO 24444 results. In the same way, HDRS-UVA-PF results can be correlated with UVA-PF values calculated from ISO 24442 as well as from ISO 24443. The importance of the inclusion of a spectral ratio of photodegradation is shown in the comparison of photostable and photounstable products. CONCLUSION: Owing to the elimination of any erythemal-relevant UVB and UVA doses, absolutely no skin reaction occurs during the HDRS experiment. Consequently, there is no need to define an MED anymore. For the first time, an alternative way to arriving at SPF and UVA-PF values is shown, without any ethical concerns of SPF testing in vivo and/or any restriction of SPF testing in vitro. Regardless of the type of formulation or the level of protection, an excellent correlation between SPFHDRSand SPF24444as for sunscreen labeling could be found. By this new alternative nonerythemal technique, not only SPF values can be measured but also UVA-PF values can be calculated with a linear correlation to ISO 24442 as well as to ISO 24443 from the same set of data. By this a robust alternative test method of SPF and UVA-PF values is described, taking into account the interaction of sunscreen formulation and skin.

Multi-laboratory study of hybrid diffuse reflectance spectroscopy to assess sunscreen SPF and UVA-PFs.

BACKGROUND: Proof-of-principle studies have established the use of Hybrid Diffuse Reflectance Spectroscopy (HDRS) methods to assess both Ultraviolet-A Protection Factor (UVA-PF) and Sun Protection Factor (SPF) indices in individual laboratories. METHODS: Multiple laboratories evaluated 23 emulsions and two spray sunscreen products to evaluate repeatability and accuracy of assessment of SPF and UVA-PF values, using HDRS test systems from various manufacturers using different designs. RESULTS: All of the laboratories reported similar SPF and UVA-PF values within a narrow range of values to establish the reliability of the HDRS methodology across laboratories, independent of equipment manufacturer or operator. CONCLUSION: HDRS test methodology provides a reliable objective instrumental estimation of sunscreen SPF and UVA-PF. These data were provided to ISO-TC217 WG7 to substantiate the ongoing development of an ISO Standard HDRS Method.

Hybrid Diffuse Reflectance Spectroscopy: Non-Erythemal in vivo Testing of Sun Protection Factor.

BACKGROUND/AIMS: In order to define a label sun protection factor (SPF) of topically applied sunscreens, in vivo test methods like ISO 24444, FDA guideline, or the Australian standard are used worldwide. The basis of all these methods is provoking an erythemal skin reaction by UV irradiation to find the level of unprotected and protected minimal erythemal doses (MED). In vitro methods replacing the human skin by any kind of non-human material are still not available. Thus, offering the new hybrid diffuse reflectance spectroscopy (HDRS) technique that is able to stay on an in vivo level for SPF testing but meanwhile neglecting the UV-dose-related erythemal skin reaction is a perfect combination to take care of sun protection and any ethical concerns in SPF testing nowadays. METHODS: HDRS is a combination of in vivo diffuse reflectance spectroscopy (DRS) measurements on the skin and in vitro transmission measurements of a sunscreen on a roughened polymethylmethacrylate plate. By this technique, the in vivo behavior of the investigated sunscreen on the skin is measured as well as the UVB absorption, which is still non-visible in the reflectance technique. In order to establish an alternative method for in vivo SPF testing, a huge number of sunscreens (80 samples) was measured by HDRS and compared to the worldwide accepted standard ISO 24444. The variety of sunscreens measured reflects a wide range of different types of formulations as well as a wide range of SPFs (5-120) to validate this new alternative SPF testing procedure. RESULTS: The applied quantity of product as well as skin color dependencies of signal generation are shown to support any basic correlation of DRS signal generation and sun protection expectations. Far-reaching statistical data analyses show an excellent link of the new non-erythemally driven HDRS-SPF technique and ISO 24444 results. In the same way, HDRS-UVA-PF results can be correlated with UVA-PF values calculated from ISO 24443. CONCLUSION: Due to the elimination of any erythemal relevant UVB and UVA doses, absolutely no skin reaction occurs. Consequently there is no need to define a MED any more. For the first time an alternative way to SPF is shown without any ethical concerns of SPF testing in vivo and/or any restriction of SPF testing in vitro. Regardless of the type of formulation or the level of protection, an excellent correlation of SPFHDRS and SPF24444 for sunscreen labeling could be found. By this new alternative non-erythemal technique, not only SPF values can be measured, but also UVA-PF values can be calculated with an excellent correlation to ISO 24443 from the same set of data. For the first time a robust alternative test method of SPF- and UVA-PF values is described, taking into account the interaction of sunscreen formulation and skin.

Influence of repetitive UVA stimulation on skin protection capacity and antioxidant efficacy.

BACKGROUND/AIMS: Topically applied antioxidants (AOs) are widely used in cosmetic products - especially in day and sun care - to help reduce oxidative stress caused by exogenous influences such as ultraviolet (UV) radiation. Despite several advances in recent years, little is known about the duration of protective effects by application of topical AOs, AO protection capacity (APC) or the activation of an endogenous protection capacity (EPC). METHODS: By measuring oxidative-stress-induced photon emission of human skin in vivo with the ICL-S method (induced chemiluminescence of human skin), the protective effect of daily AO treatment for 2 weeks was examined on 4 consecutive days after treatment. UVA-dose-independent effects were investigated by decay curve intersection point analysis. In addition, chemiluminescence signal integration was used to investigate the influence of different UVA doses for stimulation on the determined APC as well as the modulation of the EPC by repetitive UVA stimulation both forming the skin protection capacity (SPC). RESULTS: The SPC showed a strong dependency on the UVA dose used for stimulation. AO pretreatment was more effective against lower UVA doses. Over the course of 4 days, the AO-induced SPC did not change significantly for a given UVA dose. Analyzing the decay curve intersection point for 2 different UVA doses, however, revealed a decrease in SPC with time. In addition, we found that a repetitive UVA irradiation of 1 J/cm(2) caused a statistically significant protective effect against UVA irradiation by stimulation of endogenous mechanisms. CONCLUSION: Topically supplemented AOs provide a protective effect against oxidative stress for at least 3 days, supporting their widespread use in cosmetic products. Especially their interaction with cutaneous protective mechanisms should be investigated in more detail for maximal protection, as endogenous defense mechanisms are already triggered by 2 low-dose UVA irradiations within 24 h. In summary, the in vivo measurement of UVA-induced cutaneous chemiluminescence permits the UVA-dose-independent determination of the AO efficacy for better comparability of the results while also taking endogenous defense mechanisms into account.

Moisturizing and anti-sebum secretion effects of cosmetic application on human facial skin.

For human skin, high water content and low sebum secretion are considered to be main features of fair skin. To explore the proper personal care regimen for facial skin, we investigated the change of skin physiologic parameters after cosmetic application by measuring the skin water content, transepidermal water loss, and skin sebum secretion on facial skin before and after the cosmetic application using the Corneometer, Tewameter, and Sebumeter, respectively. The results indicated that the cosmetics application kept a higher water content and a lower transepidermal water loss, and at the same time, a lower sebum secretion 4 h and 8 h after the cosmetic application, compared with those before it. The situation was maintained in the succeeding three-week continuous use of the cosmetics. It could be concluded that the cosmetic application on human facial skin might provide some moisturizing effect and at the same time an anti-sebum effect, which favors the maintenance of good skin physiological function after applying skin care products. Our results might provide a scientific personal care regimen for human facial skin to prompt the balance for the hydrolipid film on skin.

Protection effect of cosmetics on human skin under simulated rigorous environment.

BACKGROUND/PURPOSE: The efficacy of cosmetics on human skin measured under normal mild laboratory environment might be discounted by exterior environment factors such as wind, UV exposure, etc. Few studies have focused on the 'genuine' efficacy of cosmetics on human skin during exposure to external rigorous environment. The aim of this study was to develop a model for the evaluation of the efficacy of cosmetics on human skin under simulated rigorous environment. METHODS: We measured skin water content and transepidermal water loss (TEWL) before and after products application under simulated windy and sub-erythema UV exposure treatment in a constant temperature and humidity laboratory. RESULTS: The results showed that the products had higher water content and lower TEWL at 2, 4 and 8 h of products application, and ameliorated the skin moisturization situation after a 3-week continuous use of the products. In addition, the products might protect the skin to maintain the normal water content and TEWL under the simulated windy or sub-erythema UV exposure treatment in our laboratory when compared with untreated area. CONCLUSION: Our data indicate that this model may provide a more accurate evaluation for the genuine moisturizing effect of cosmetics under external natural climate.

Moisturizing and antisebum effect of cosmetic application on facial skin.

BACKGROUND: Water content of the stratum corneum and skin surface lipids are important factors in the appearance and function of skin. High water content and low sebum secretion are considered main features of fair skin. Aim This paper aims to study the change of skin physiological parameters after cosmetic application. METHODS: The skin water content, transepidermal water loss, and skin sebum secretion on different regions of the facial skin before and after the cosmetic application were measured using Corneometer, Tewameter, and Sebumeter, respectively. RESULTS: The cosmetics kept higher water content and lower transepidermal water loss, at the same time lower sebum secretion 4 and 8 h after the cosmetic application, compared with those before it. The situation was maintained in the following 3-week continuous use of the cosmetics. CONCLUSION: The cosmetic application on human facial skin could provide some moisturizing effect and at the same time some antisebum effect according to different regions on facial skin, which favored the maintenance of good skin physiological function after applying skin care products.