The environmental dimension of acne: a comprehensive evidence synthesis from epidemiology to molecular pathogenesis

Acne vulgaris is a highly prevalent chronic inflammatory skin disease. Its pathogenesis has traditionally focused on sebum overproduction, follicular hyperkeratinization, cutibacterium acnes colonization, and the ensuing inflammatory response. However, the skin is not merely a passive barrier but an active endocrine organ highly sensitive to external environmental cues. Accumulating evidence now indicates that a wide array of environmental exposures plays a significant role in the pathophysiology of acne. This narrative review comprehensively synthesizes current evidence, revealing air pollutants—particularly fine particulate matter (PM 2.5 , PM 10 ) and nitrogen dioxide (NO 2 )—as established risk factors that precisely target the core pathological processes of acne by inducing oxidative stress, compromising skin barrier integrity, and exacerbating inflammatory cascades. Macro-climatic factors (temperature, humidity, ultraviolet radiation) directly modulate sebaceous gland activity and the cutaneous microenvironment, shaping the disease's distinct geographical and seasonal patterns. Furthermore, endocrine-disrupting chemicals (EDCs), such as bisphenol A and polycyclic aromatic hydrocarbons, can mimic or antagonize hormonal signaling, thereby broadly dysregulating the endocrine networks governing sebum production and follicular differentiation. Despite these advances, significant research gaps remain. Epidemiological evidence shows regional heterogeneity; direct studies on specific exposure sources like the built environment, heavy metals and electronic device-emitted blue light are relatively scarce; the translation of mechanistic discoveries into clinical biomarkers and targeted interventions is inadequate; and understanding of the combined effects of real-world pollutant mixtures and individual-environment interactions is superficial. Future research must adopt prospective cohort designs and an exposomic framework, integrated with multi-omics technologies, to elucidate causal relationships, identify susceptibility biomarkers, and ultimately advance the development of precise prevention and management strategies based on well-defined mechanisms (e.g., AhR pathway activation, oxidative stress, or skin microbiome dysbiosis). Integrating environmental health perspectives into the etiological understanding and clinical management of acne is crucial for achieving more effective disease prevention and control.