Abstract
Skin is our barrier against environmental damage. Moisturizers are widely used to increase hydration and barrier integrity of the skin; however, there are contrasting observations on their in vivo effects in real-life settings. In cosmetic studies, corneometers and tewameters are traditionally used to assess skin hydration. In this study, two novel noninvasive diagnostic techniques, optical coherence tomography (OCT) and confocal Raman spectroscopy, were used to analyze stratum corneum and epidermal thickness (ET), water content, blood flow in function of depth, skin roughness, attenuation coefficient, natural moisturizing factor, ceramides and free fatty acids, cholesterol, urea, and lactates in 20 female subjects aged between 30 and 45 before and after 2 weeks application of a commercially available moisturizing lotion on one forearm. The untreated forearm served as control. A third measurement was conducted 1 week after cessation of moisturizing to verify whether the changes in the analyzed parameters persisted. We noticed a reduction in skin roughness, an increase in ceramides and free fatty acids and a not statistically significant increase in ET. As a conclusion, short time moisturizing appears insufficient to provide significant changes in skin morphology and composition, as assessed by OCT and RS. Novel noninvasive imaging methods are suitable for the evaluation of skin response to topical moisturizers. Further studies on larger sample size and longer treatment schedules are needed to analyze changes under treatment with moisturizers and to standardize the use of novel noninvasive diagnostic techniques.
Highlights
Skin has a crucial role as a barrier against environmental factors and must be regularly hydrated for protecting its integrity and function
The integrity of the skin is needed to preserve water in the epidermis, which is essential for hydrolytic enzymatic reactions in keratinocytes and maintaining the defence function against microorganisms, chemicals, and mechanical stress
Occlusive moisturizers function as a water-impermeable barrier over the skin surface, thereby preventing Transepidermal water loss (TEWL) and creating an optimal environment for restoration of the stratum corneum (SC) barrier
Summary
Skin has a crucial role as a barrier against environmental factors and must be regularly hydrated for protecting its integrity and function. Its complex structure is composed of corneocytes, their hygroscopic material, collectively referred to as natural moisturizing factor (NMF), and an intercellular lipid bilayer matrix. NMF is the degradation product of filaggrin, acting as an efficient humectant and containing amino acids, ceramides, cholesterol, and fatty acids. If SC water content reduces to a critical level, normal desquamation is impaired, leading to the accumulation of corneocytes on the skin surface and causing the appearance of dryness and scaling.[1]. Moisturizers increase skin hydration and re-establish skin lipid film after cleansing; they can function as vehicles to deliver active ingredients into the skin.[1]
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