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The physical barrier of the stratum corneum (SC) is provided by corneocytes and the lateral organization of intercellular lipids, which necessarily includes the orthorhombic organization phase. A review of methods used for in vivo non-invasive measurement of skin barrier function has been carried out and it has been shown that all currently used methods are indirect. The most popular method is the measurement of the transepidermal water loss (TEWL), which does not provide information on biophysical parameters responsible for the barrier function of the SC. It has been shown that confocal Raman microspectroscopy is the most suitable non-invasive method to determine the depth profile of the lateral organization of intercellular lipids, i.e. to study the skin barrier function in vivo.

The COVID‐19 pandemic underscored the crucial importance of enhanced indoor air quality control measures to mitigate the spread of respiratory pathogens. Far‐UVC is a type of germicidal ultraviolet technology, with wavelengths between 200 and 235 nm, that has emerged as a highly promising approach for indoor air disinfection. Due to its enhanced safety compared to conventional 254 nm upper‐room germicidal systems, far‐UVC allows for whole‐room direct exposure of occupied spaces, potentially offering greater efficacy, since the total room air is constantly treated. While current evidence supports using far‐UVC systems within existing guidelines, understanding the upper safety limit is critical to maximizing its effectiveness, particularly for the acute phase of a pandemic or epidemic when greater protection may be needed. This review article summarizes the substantial present knowledge on far‐UVC safety regarding skin and eye exposure and highlights research priorities to discern the maximum exposure levels that avoid adverse effects. We advocate for comprehensive safety studies that explore potential mechanisms of harm, generate action spectra for crucial biological effects and conduct high‐dose, long‐term exposure trials. Such rigorous scientific investigation will be key to determining safe and effective levels for far‐UVC deployment in indoor environments, contributing significantly to future pandemic preparedness and response. [ABSTRACT FROM AUTHOR]

The main components of the stratum corneum (SC), water, lipids, and proteins, are non‐homogeneously distributed throughout the depth. The quantitative determination of their concentration profiles and penetration depth of topically applied substances are urgent topics of dermatological and cosmetic research. Confocal Raman micro‐spectroscopy has distinct advantages when determining semi‐quantitative concentrations of SC components and topically applied substances non‐invasively and in vivo. In this work, we applied a tailored multivariate curve resolution‐alternating least squares (tMCR‐ALS) method to analyze Raman spectra of the SC in the 2000–4000 cm−1 region for quantitatively determining the concentrations of water, lipids, proteins, and topically applied oils using substance‐related spectral loadings which were allowed to change depth‐dependently from the SC's surface toward its bottom. tMCR‐ALS makes matching of depth‐dependent signal attenuation, that is, the normalization on keratin, unnecessary and requires only a few additional experiments for calibration – Raman spectra of the pure materials and their densities. [ABSTRACT FROM AUTHOR]

Fungal infections have increased considerably over the last decades, becoming progressively resistant to common drugs. UVC light has shown microbiological eradication effects, whereby the wavelength of 254 nm is strongly carcino‐ and mutagenic. Therefore, 222 and 233 nm, which do not significantly harm skin cells, were tested for their antifungal effects. Microbicidal doses were reached at 40 mJ/cm2 for both wavelengths, resulting in only minor superficial skin damage (<20 μm). UVC irradiation with far‐UVC <240 nm represents a new opportunity to effectively eradicate even larger pathogens on tissue causing no or strongly reduced DNA and tissue damage. [ABSTRACT FROM AUTHOR]

This aim of this study was to evaluate the penetration depth, antioxidant capacity and the clinical efficacy of Melaleuca alternifolia pure essential oil and in a nanoemulsion to prevent skin photoaging. For this, 2% of pure essential oil or 2% of this essential oil in a nanoemulsion were vehiculated in a formulation. The skin penetration was evaluated using confocal Raman microspectroscopy. The radical protection factor was evaluated using electron paramagnetic resonance spectroscopy. For a clinical study, 40 male participants, aged 18–28 years, were enrolled, being divided into three groups: vehicle formulation, M. alternifolia pure essential oil and M. alternifolia Nanoemulsion. All the participants also received a sunscreen SPF 50 to use during the day. Before and after 90 days of study, skin hydrolipidics and morphological characteristics were performed by skin imaging and biophysical techniques. The nanoemulsion presented a lower antioxidant capacity and a higher penetration through the stratum corneum, reaching the viable epidermis, improving the stratum granulosum morphology. The groups presented an increase in the papillary depth, improving in the dermis echogenicity and the collagen fibers. Melaleuca alternifolia essential provides the potential to improve photoaged skin, being the application of nanoemulsion able to reach deeper skin layers. [ABSTRACT FROM AUTHOR]