Search

Background/purpose Near-infrared ( NIR) light with high water absorption enables us to visualize the water content distribution appeared in the superficial skin layer. The light penetration depth with the wavelength of 1920 nm is almost 100 μm from the skin surface. Thus, the water distribution in the stratum corneum can be effectively imaged by detecting the wavelength band around 1920 nm. The aim of this article was to measure the time-lapse behavior of the tiny droplet of the moisturizer spreading on the skin surface by imaging in 1920 nm wavelength band for investigating the correlation with the traditional index of the skin condition such as the water content and transepidermal water loss ( TEWL). Methods Experiment is performed with three moisturizer products and seven volunteer subjects. The NIR image is acquired by an originally designed imaging scope equipped with the white light of the strong brightness [super continuum (SC) light], the bandpass filter with the center wavelength of 1920 nm, and the NIR image sensor. A tiny droplet of the moisturizer is put on the surface of the skin and the time-lapse images are saved. Each acquired image is analyzed from a view point of the droplet area and elapsed time for absorption into the skin. The water content and TEWL of all subjects are measured by the conventional electrical method for investigating the relationship with the measured droplet dynamics parameters. Results Elapsed time for moisturizer droplet to be absorbed into the skin, the droplet area just before absorption for three moisturizer products, skin water contents, and TEWL for seven subjects were measured and correlation coefficients for each parameters were calculated. It was found that the skin with higher water contents or lower TEWL absorbed the moisturizer faster and spreads moisturizer wider. Also absorption and spreading speed depend on moisturizer property (moisturizing or fresh) which is originated from the moisturizer constituents. Conclusion The correlation values between the moisturizer dynamics on the skin surface and the traditional index of the skin property were clarified. It was found that the skin with the high water content or low TEWL absorbs the moisturizer droplet fast. The spreading area depends not only on the skin property but on the constituents of the moisturizers. [ABSTRACT FROM AUTHOR]

Background/purpose As urea is one of the natural moisturizing factor ( NMF) components in the stratum corneum, it has been used in topical products to improve skin conditions. However, the penetration behavior of urea in the skin after application of urea-containing cream has not been determined as there has been no technique with which to measure the urea content in the skin in vivo non-invasively. We therefore applied Raman spectroscopy to evaluate the depth profile of urea content in the skin. We investigated changes in depth profiles of two forms of urea to evaluate the penetration behavior of urea after application of urea-containing cream. Methods Commercially available moisturizing creams F and R in quantities of 2.2-mg/cm2 and containing 20% (w/w) urea were applied to volar forearm skin of six Japanese subjects. Raman spectra of the skin were measured at 2-μm intervals from the skin surface toward the interior using a confocal Raman spectrometer (model 3510 SCA) before and 15, 60, and 120 min after the application of the creams. The amounts of the two forms of urea, urea in water solution and urea in a solid state, were calculated by adding the spectra of solid urea and the cream base to a previously reported algorithm including the spectrum of urea in water solution. Results The characteristic band of urea in water solution was observed at approximately 1004/cm and that of the solid state at approximately 1010/cm in the Raman spectra of the skin after application of either cream. There was more urea in water solution form in the area where cream F was applied than in the area where cream R was applied. There was more urea in a solid state in the area where cream R was applied than in the area where cream F was applied at all depths and measurement times. In particular, there was significantly more urea in a solid state below a depth of 2 μm in the area where cream R was applied than in the area where cream F was applied 15 min after application. Conclusion The present study demonstrated that we can measure both urea forms in the skin after the application of urea-containing creams. The proposed technique would be useful in the evaluation of characteristics of the penetration behavior of urea in the skin after the application of various urea-containing moisturizers. [ABSTRACT FROM AUTHOR]