A novel in vivo test method for evaluating the infrared radiation protection provided by sunscreen products

Carotenoids in Human SkinIn Vivo: Antioxidant and Photo-Protectant Role against External and Internal Stressors

The antioxidant system of the human body plays a crucial role in maintaining redox homeostasis and has an important protective function. Carotenoids have pronounced antioxidant properties in the neutralization of free radicals. In human skin, carotenoids have a high concentration in the stratum corneum (SC)-the horny outermost layer of the epidermis, where they accumulate within lipid lamellae. Resonance Raman spectroscopy and diffuse reflectance spectroscopy are optical methods that are used to non-invasively determine the carotenoid concentration in the human SC in vivo. It was shown by electron paramagnetic resonance spectroscopy that carotenoids support the entire antioxidant status of the human SC in vivo by neutralizing free radicals and thus, counteracting the development of oxidative stress. This review is devoted to assembling the kinetics of the carotenoids in the human SC in vivo using non-invasive optical and spectroscopic methods. Factors contributing to the changes of the carotenoid concentration in the human SC and their influence on the antioxidant status of the SC in vivo are summarized. The effect of chemotherapy on the carotenoid concentration of the SC in cancer patients is presented. A potential antioxidant-based pathomechanism of chemotherapy-induced hand-foot syndrome and a method to reduce its frequency and severity are discussed.

In vivo determination of the Infrared-A protection factor on human skin

BACKGROUND

Chronic exposure to infrared A (IR-A) irradiation causes photoaging. However, daily or acute exposure to IR-A rarely induces erythema or pigmentation. Thus, evaluation of the physiological changes taking place on the skin surface is insufficient for clinical investigations.

MATERIALS AND METHODS

We fabricated a novel device to obtain the IR-A protection factor (IPF) on human skin. This device consists of an artificial light source that mimics the actual IR-A intensity of sunlight, and a spectrophotometer to measure the spectral reflectance on the skin surface. The IPF can be determined by measuring the difference in spectral reflectance on the skin before and after the use of products and can be verified by the statistical criterion. A validation study was performed using different light intensities and two experimenters. Finally, we monitored the IPF on 12 commercial cosmetics.

RESULTS

After considering the IPF and L*-values, we selected the optimal sample and performed a validation study. Neither the intensity of IR-A irradiation or the experimenters significantly affected the IPF. 12 commercial products exhibited their own IPF values and were verified by statistical criteria, with one exception.

CONCLUSION

The present IPF evaluation method was concluded to be robust and reliable. This method is simple and safe for the subjects, and could be helpful for the development of IR-A protection products and the confirmation of product performances.