Use of reflectance near-infrared spectroscopy to investigate the effects of daily moisturizer application on skin optical response and barrier function

Abstract

Citation: Qassem, M. & Kyriacou, P. A. (2014). Use of reflectance near-infrared spectroscopy to investigate the effects of daily moisturizer application on skin optical response and barrier function. Journal of Biomedical Optics, 19(8), 087007. doi: 10.1117/1. JBO.19.8.087007 This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract. A number of noninvasive techniques and instruments have emerged over the years allowing much progress toward clarifying the structure and function of human skin and studying the effects of various applied substances. All of this research has provided great insight into the interactions between skin and various products through quantitative and qualitative measurements. Such methods include near-infrared spectroscopy (NIRS), a technique which has gained popularity over the years and has often been employed to accurately determine the moisture levels and water content of skin based on its sensitivity to hydrogen bonding. NIRS has also been applied in many studies to report the efficacy of moisturizing products and assess their benefits to the skin. However, many of these studies have reported an increase in skin water content following moisturizer application while some have challenged the benefits of long-term moisturizer use, particularly on normal skin, and even suggested that it can increase the skin's susceptibility to irritants. This paper reports the results of a pilot in vivo study carried out on the skin of 20 healthy volunteers, categorized into groups depending on their skin type and frequency of moisturizer use, in order to investigate the optical response of human skin after direct short-term contact with water followed by application of a moisturizer. The measurements were obtained using a highly advanced spectrophotometer in the region of 900 to 2100 nm equipped with a customized reflectance fiber optic handheld probe. Scatter graphs of group results and second derivative spectra have shown an interesting pattern between frequent users of moisturizers and individuals who do not use moisturizers, suggesting that long-term daily moisturization may have an effect on skin barrier function. The results also raise some questions regarding the optical characteristics of different skin types, as well as the varying response between different water bands in the NIR region. Future work will focus on gaining more knowledge about these subjects and obtaining results from a larger population, as well as performing statistical analysis through regression methods in order to further improve optical skin measurements. Permanent

Review of Modern Techniques for the Assessment of Skin Hydration

“…Exceptions to this are NIR spectroscopy and OTTER. NIR spectroscopic instrumentation can be easily coupled with flexible fibre optics and portable spectrometers for reduced costs and restrictions on selection of examination site, and can offer increased stability against environmental conditions such as temperature and relative humidity [248, 250,257]. Moreover, techniques such as ATR-IR are occlusive, which can cause accumulation of water at the test site, and as for OCT, the coherence length is short, and resolution can be less than 10 µm.…”

“…Finally, a series of studies by Qassem et al [250][251][252][253] combined NIR data with both PCR and PLS techniques and found clear spectral differences associated with frequency of moisturiser use ( Figure 6), and highlighted the possibility of using this technique to detect changes in barrier function by measuring water penetration after wet patch testing. The authors suggested that NIR spectroscopy can provide comprehensive skin analysis in a fast and simple manner.…”

Reflectance near-infrared measurements for determining changes in skin barrier function and scattering in relation to moisturizer application

“…As for the NIR skin spectra, the same instrumental settings described in our previous publication 18 were maintained in order to avoid changes relating to technical differences.…”

“…Using this information, it can be assumed that changes to skin barrier function can be detected by monitoring differences in absorption at the two bands over time. In a previous study, 18 we used principal component analysis (PCA) to demonstrate a clear link between separation and randomization of PCA scores with the frequency of moisturizer application. Additionally, in a pilot study implementing a different protocol, 19 similar results were obtained, and the change in absorption intensity at the 1450 and 1900 nm bands prior to and following regular moisturizer application were taken to suggest that long-term moisturizer use had limited water uptake from deeper penetration.…”

Measurement of dermal water content using a multi-wavelength optical sensor

“…Water, in particular, has several prominent absorption peaks in the NIR spectrum. These properties can be used to deduce information pertaining to various aspects of skin health [8,9,10,11]. Interestingly, it is possible to differentiate between bound and free water inside the skin [12].…”