Editorial: Advancements in human skin photobiology: exploring the intricate relationship between human skin and light

Human skin is continuously exposed to electromagnetic radiation spanning ultraviolet (UV), visible light (VL), and longer wavelengths. These exposures regulate immune signaling, pigmentation, carcinogenesis, vascular biology, and therapeutic response. While UV-induced DNA damage remains central to photobiology, growing evidence demonstrates that cutaneous responses to light extend beyond mutagenesis and involve complex inflammatory, pigmentary, and photochemical pathways. This Research Topic brings together mechanistic, methodological, and translational studies that collectively expand our understanding of wavelength-specific skin biology and its clinical implications.A key mechanistic contribution is provided by Lesiak et al., who investigate the role of NLRP1 and NLRP3 inflammasomes and IL-33 in ultraviolet-induced cutaneous carcinogenesis. Using keratinocyte models exposed to UVA and UVB radiation, the authors demonstrate dosedependent upregulation of IL-33, IL-18, and IL-1β. Silencing NLRP1 or NLRP3 attenuated cytokine expression and altered tumor-associated marker profiles, supporting a role for inflammasome signaling in shaping a pro-tumorigenic inflammatory microenvironment. This work reinforces the concept that photocarcinogenesis is driven not only by genomic damage but also by immune modulation and cytokine signaling.Expanding beyond UV-centric paradigms, Bardhi et al. examine methodological approaches for evaluating VL + long wavelength UVA1 (LWUVA1) induced pigmentation in individuals with skin of color. Comparing Investigator's Global Assessment (IGA), diffuse reflectance spectroscopy (DRS), and MART-1 immunohistochemistry, the authors demonstrate that noninvasive assessments were more sensitive in detecting persistent pigment darkening than invasive biopsy-based markers. Their findings underscore the importance of standardized, biologically relevant testing frameworks in VL photobiology and have implications for sunscreen efficacy evaluation in darker phototypes.The translational application of photobiology is exemplified by Wang et al., who evaluate hemoporfin-mediated photodynamic therapy (HMME-PDT) for port wine stains in children with prior pulsed dye laser (PDL) treatment. In a cohort of 216 patients, prior PDL exposure did not significantly impact HMME-PDT efficacy or safety. Importantly, dermoscopic vascular features and lesion location influenced outcomes, highlighting the value of integrating vascular morphology into therapeutic planning. This study illustrates how understanding wavelengthspecific photochemical activation can refine vascular-targeted therapies beyond traditional photothermolysis.Finally, Aguilera et al. provide a quantitative and qualitative evaluation of UV-indicating photochromic devices. Using a calibrated solar simulator and colorimetric analysis, the authors demonstrate that commercially available photochromic bracelets rapidly saturate at low UV index values and cannot reliably differentiate between varying radiation intensities or spectral bands. Moreover, activation occurred under both UVA and high-energy VL. These findings raise important considerations regarding the limitations of consumer-based UV indicators and the need for accurate photoprotection education tools.Collectively, the contributions in this Research Topic highlight several overarching themes. First, cutaneous responses to light are highly wavelength-specific and biologically contextual. From inflammasome-mediated cytokine activation to VL-induced persistent pigmentation and photochemical vascular targeting, skin and light interactions extend well beyond UV-induced mutagenesis. Second, methodological rigor is critical in advancing photobiology. Whether evaluating pigmentation endpoints or assessing consumer UV indicators, standardized and biologically relevant measurement strategies are essential to ensure translational accuracy. Third, mechanistic insights directly inform clinical innovation. Understanding inflammasome pathways may identify targets for modulating photocarcinogenesis, while refined knowledge of spectral responses improves photodynamic and vascular laser therapies. Similarly, rigorous assessment of UV detection devices informs public health messaging and photoprotection strategies.As VL gains recognition as a biologically relevant spectrum, expanding photobiological frameworks beyond UV radiation alone is imperative. Continued interdisciplinary collaboration across molecular biology, dermatology, biomedical optics, and public health will be essential to translate mechanistic discoveries into improved preventive and therapeutic approaches. This collection stimulates further investigation into the complex and dynamic relationship between human skin and light, fostering innovations that enhance skin health across diverse phototypes and exposure environments.