Background: The influence of various environmental factors on skin properties is well known. However, there is a lack of research into the effect of quarantine masks on skin properties, even though the use of masks has significantly increased after the COVID‐19 outbreak. Therefore, this study aimed to investigate the influence of mask use on skin properties.Materials and Methods: Twenty subjects were enrolled in this study. The subjects used approved quarantine masks for 6 hours a day for 2 weeks. We measured eight skin biophysical parameters: temperature, redness, pore volume, texture, elasticity, trans‐epidermal water loss (TEWL), sebum content, and pH, and evaluated acne lesions before and after using quarantine masks. The evaluation was performed on the mask‐wearing area of the face.Results: Skin temperature, redness, and TEWL increased significantly after a 6‐hour mask use, while the sebum content increased marginally. Skin elasticity was reduced by the use of masks over 1 and 2 weeks, whereas the pore volume and the number of acne lesions increased after a 2‐week mask use. The skin changes caused by mask use showed sex‐based differences in the skin elasticity (after 6 hours), redness, and roughness (after 2 weeks).Conclusions: The use of quarantine masks causes a change in the skin temperature, redness, and TEWL in the short term and in skin elasticity, pores, and acne in the long term. This study revealed that prolonged mask use could have negative effects on the skin.

Background/Objectives: Enhancement of cellular NAD⁺ mediated by NMN has emerged as a pivotal strategy in modulating the aging process. This study aimed to systematically investigate the anti-aging effects of NMN on human skin fibroblasts, focusing on how the former contributes to the improvement of cellular health and function. This study elucidated the molecular and functional mechanisms by which NMN contributes to the attenuation of skin aging. Methods: We performed extensive in vitro and transcriptomic analyses. Human skin fibroblasts were treated with NMN, and the induced biological responses were observed under oxidative stress/photo-aging models. Results: Transcriptome analysis revealed distinct gene expression patterns for NAD⁺ and its precursors (NMN, NR, and NAM), showing significant differences between NMN and other precursors (NR and NMN). NMN seemed to be significantly involved in cytokine and chemokine activity. It significantly elevated cellular NAD⁺ levels, activated sirtuin and autophagy pathways, and enhanced mitochondrial function, collectively maintaining cellular homeostasis under stress. Furthermore, it suppressed cellular senescence, promoted cell proliferation, supported extracellular matrix integrity, and accelerated wound healing. Conclusions: The study provided essential mechanistic evidence supporting the anti-aging effects of NMN in skin cells and addressed the current lack of scientific validation of NMN-based topical applications. The findings established a solid academic background for future translational research and the development of NMN-based therapeutics and cosmeceuticals.

Background: Skin pores are structural features of the skin, which tend to change as the skin ages. Since previous studies measured pores two‐dimensionally, precise measurements using three‐dimensional imaging were needed to comprehensively understand skin pores. This study aimed to determine the patterns behind the changes in skin pores during one's lifetime and to identify new characteristics of the pores in aged.Materials and Methods: Skin surface profiles were measured three‐dimensionally from the cheeks of 101 Korean women from February to March 2020 to analyze the exact state of their pores. The researchers performed K‐means clustering to classify the skin pores, and topographical features of pores were analyzed as well. Statistical analyses were performed to verify the differences in the skin pore characteristics among clusters and the correlation between clusters and ages.Results: Skin pores were classified into five groups based on size, density, and elongation. The skin conditions of the cluster groups were well correlated with aging, despite excluding age as a factor in pore classification. Adjacent skin pores tend to connect in the elderly.Conclusion: Skin pores become larger and longer over time. Skin pores connect together in the elderly, which might be related to wrinkle formation. This phenomenon strongly suggests skin pores as a characteristic of aging skin and as a potential target for anti‐aging treatment.

Background: The stratum corneum (SC), the outermost layer of the skin epidermis, acts as an effective bi‐directional barrier, preventing water loss (inside–outside barrier) and entry of foreign substances (outside–inside barrier). Although transepidermal water loss (TEWL) is a widely‐used measure of barrier function, it represents only inside‐outside protection. Therefore, we aimed to establish a non‐invasive method for quantitative evaluation of the outside–inside barrier function and visually present a skin barrier model. Materials and methods: Skin barrier damage was induced by applying a closed patch of 1% sodium dodecyl sulfate to the forearms of eight participants; they were instructed to apply a barrier cream on a designated damaged area twice daily for 5 days. The SC barrier was evaluated by measuring TEWL and fluorescein sodium salt penetration rate before, immediately after, and 5 days after damage. The penetration rate was assessed using tape‐stripping (TS) technique and fluorescence microscopy. Results: The rates of fluorescein sodium salt penetration into the lower layers of SC differed significantly based on the degree of skin barrier damage. The correlation between penetration rate and TEWL was weak after two rounds of TS and became stronger after subsequent rounds. Five days after skin barrier damage, the penetration rate of all layers differed significantly between areas with and without the barrier cream application. Conclusion: Our findings demonstrated that the penetration rate was dependent on skin barrier conditions. The penetration rate and corresponding fluorescence images are suitable quantitative indicators that can visually represent skin barrier conditions.

Background: With growing interest in hair health, researchers are exploring aspects beyond the surface qualities of hair, such as its porous inner structure. While previous studies have focused on the effects of treatments such as perming and hair dying on hair porosity, less emphasis has been paid to the effects of harmful environmental factors such as ultraviolet (UV) rays and particulate matter on the porous nature of hair.Aims: The aim of this study was to bridge this gap by investigating how UV rays and particulate matter affect hair porosity in different ways. Our study could help elucidate how these external factors influence hair health and shed light on previously unknown aspects of hair porosity.Methods: Hair tresses were bleached, cut into 1 cm‐long sections, and stained with methylene blue. The sections were then irradiated with UV light or exposed to particulate matter.Results: Bleached hair absorbed more methylene blue than normal hair. UV radiation‐induced hair porosity occurred at 3 h after irradiation and increased with time. Particulate matter alone did not affect the porosity of the damaged hair; however, in combination with UV irradiation, it substantially increased hair porosity.Conclusion: Environmental challenges such as a depleted ozone layer and increasing pollution may increase hair porosity, which can be prevented by maintaining healthy hair.

Skin barrier dysfunction and thin epidermis are hallmarks of sensitive skin and contribute to premature aging. Avenanthramides are the primary bioactive components of colloidal oatmeal, a commonly used treatment to enhance skin barrier function. This study investigated the relationship between skin barrier function and epidermal characteristics and explored the potential of dihydroavenanthramide D (dhAvD), a synthetic avenanthramide, to improve the skin barrier. We observed a significant correlation between impaired skin barrier function and decreased epidermal thickness, suggesting that a weakened barrier contributes to increased sensitivity. Our in vitro results in HaCaT cells demonstrated that dhAvD enhances keratinocyte proliferation, migration, and tight junction protein expression, thereby strengthening the skin barrier. To mimic skin barrier dysfunction, we treated keratinocytes and full-thickness skin equivalents with IL-4 and IL-13, cytokines that are implicated in atopic dermatitis, and confirmed the downregulation of tight junction and differentiation markers. Furthermore, dhAvD treatment restored the barrier function and normalized the expression of key epidermal components, such as tight junction proteins and natural moisturizing factors, in keratinocytes treated with inflammatory cytokines. In the reconstructed human skin model, dhAvD promoted both epidermal and dermal restoration. These findings suggest that dhAvD has the potential to alleviate skin sensitivity and improve skin barrier function.