Human hair, particularly on the scalp, serves as a significant aspect of social identity and well-being. The exposome, encompassing both intrinsic and extrinsic factors, plays a fundamental role in hair weathering. Intrinsic factors include genetic predispositions and physiological changes within the body, while extrinsic factors comprise environmental exposures such as UV radiation, pollution, humidity, temperature variations, lifestyle choices, and chemical treatments. These elements collectively contribute to the cumulative damage experienced by hair over time. Understanding the comprehensive impact of the exposome on hair health and hair aging necessitates an exploration of various environmental conditions, lifestyle factors, and technical artifacts. Despite advancements in research, the intricate mechanisms underlying the exposome influence on hair remain incompletely understood. Through a comprehensive review of current literature and emerging research findings, this study aims to enhance the understanding of exposome impact on hair health.

Skin aging is a complex, continuous, multifactorial process resulting from cumulative morphological and functional changes in the skin over time.This happens because of 2 processes: intrinsic and extrinsic skin aging. Intrinsic skin aging occurs naturally over time and reflects each person's genetic makeup, or heredity. Extrinsic skin aging, on the other hand, is due to exposomal factors, such as solar radiation, air pollution, tobacco or nutrition, being the first 2 the most important of all. Exposure to air pollutants, primarily gases such as ground-level ozone and particulate matter, can accelerate the process via 4 key mechanisms: reactive oxygen species generation, inflammation, skin microbiome disruption, and aryl hydrocarbon receptor activation. Regarding solar radiation, all wavelengths reaching the Earth's surface have an impact on the skin, having a synergistic effect with air pollution ("photo-pollution"). Here, we discuss this phenomenon and mitigation strategies, including sunscreens, cosmetics with film-forming plus antioxidant ingredients, and oral supplementation.

Onychomycosis, a fungal nail infection, affects about 4% of the global population. Current topical antifungals like ciclopirox and amorolfine have limited effectiveness, highlighting the need for better treatments. WSNS-PO is a novel water-soluble therapy designed to treat and prevent onychomycosis by enhancing nail health. This study evaluated WSNS-PO’s ability to penetrate the nail plate and to treat and prevent infection by Trichophyton rubrum using bovine hoof membranes and human nail clippings. The anti-fungal efficacy of WSNS-PO was additionally evaluated against other dermatophytes, non-dermatophyte fungi, and yeast. The results showed that WSNS-PO effectively permeated nails and reduced and prevented the colonization of human nail fragments by T. rubrum ex vivo, demonstrating an efficacy comparable to ciclopirox and amorolfine. WSNS-PO also prevented the transfer of T. rubrum infection between nails and inhibited the fungal colonization of human skin by dermatophyte and non-dermatophyte fungi and yeast. Together, these results indicate that WSNS-PO possesses fungistatic, barrier-forming, and anti-adhesive properties, suggesting that it holds promise as an onychomycosis treatment against dermatophytes, yeast, and molds.

Hair holds a significance that surpasses mere aesthetics, as it plays a pivotal role in our social interactions and contributes significantly to the definition of our self-esteem. Central to this understanding is the concept of the exposome, which encompasses intrinsic elements like genetics and physiological changes, as well as extrinsic factors such as UV radiation, pollution, lifestyle choices, and chemical treatments. These factors may significantly impact hair health and hair aging. Expanding upon the groundwork laid by the first part of this research (Cedirian et al., 2024), this study aims to deepen our understanding of exposome influence on hair. Specifically, through a narrative review of current literature, this second part endeavors to provide non-pharmacological treatment solutions and effective strategies to mitigate the negative impact of the exposome on hair health.