Biological rhythms, sleep disturbances, and the skin - a narrative review.
Sleep, circadian rhythms, light exposure, and environmental factors are increasingly recognized as important regulators of skin physiology. The skin contains peripheral clocks and exhibits circadian rhythmicity in barrier function, immune activity, pigmentation, temperature, blood flow, and repair processes. This review aims to summarize the current evidence linking sleep disturbances, circadian regulation, light exposure, seasonal variation, environmental temperature, and circadian desynchronization with skin physiology and some dermatoses. Sleep loss and disturbances in sleep duration may alter immune function and impair skin barrier integrity, potentially contributing to inflammatory dermatoses, including atopic dermatitis, psoriasis, and eczema. Light is the principal synchronizer of biological rhythms, whereas light at night, jet lag, and shift work may disrupt circadian organization, alter melatonin secretion, and impair central and peripheral clock regulation. These disturbances may be relevant to skin aging, impaired repair, inflammatory skin diseases, and potential skin carcinogenesis. Further studies are needed to better understand how circadian disruption influences skin homeostasis, repair processes, and disease development.