Melanocyte-Fibroblast Crosstalk Under Visible Light and Infrared-A Exposure: A Narrative Review of Implications for Photoaging and Dyschromia.

Solar radiation extends beyond the ultraviolet spectrum to include visible light and infrared-A wavelengths, which have traditionally been considered biologically inert. Emerging evidence indicates that these longer wavelengths act both independently and in combination to influence communication between skin cells, contributing meaningfully to photoaging and pigmentary changes. This narrative review synthesizes existing peer-reviewed research on how visible light and infrared-A radiation alter signaling between dermal and epidermal cells and how these alterations may underlie disorders of pigmentation and structural skin aging. A structured search of PubMed and Scopus (January 2016-June 2026) was conducted to identify English-language, peer-reviewed studies examining the mechanisms by which these wavelengths affect skin cell biology and intercellular communication, encompassing in vitro, ex vivo, animal, and clinical research. The synthesized findings indicate that visible light and infrared radiation jointly influence cellular signaling pathways that govern pigment production, breakdown of the skin's structural matrix, and cellular aging processes. Accumulating, predominantly preclinical evidence suggests that these wavelengths should no longer be overlooked in the study of skin biology's response to sunlight. Accumulating evidence points to distinct and overlapping mechanisms by which each spectral range promotes cellular aging, structural matrix changes, and disruption of the signaling molecules that dermal cells use to regulate pigment-producing cells in the skin's outer layer. This disruption alters key communication factors that drive overactivation of pigment cells, resulting in uneven pigmentation. A separate mechanism, independent of this cell-to-cell communication pathway, involves direct activation of pigment-producing cells by visible light through a distinct cellular signaling cascade. These findings suggest that broadening photoprotection beyond the ultraviolet range may be a reasonable strategy, while also identifying candidate, largely investigational therapeutic targets for addressing photoaging and pigmentary disorders that require further clinical study.