Biological effects of blue light on cultured keratinocytes - a systematic review.

BACKGROUND

Keratinocyte in vitro studies using blue light photobiomodulation report divergent findings regarding cytotoxicity and viability. This systematic review synthesizes evidence from keratinocyte cultures and maps blue light photobiomodulation.

METHODS

Original articles published between 1990 and 2026 were identified through PubMed, Embase, Web of Science, and the Cochrane Library and imported into Covidence. Eligible studies evaluated primary or immortalized keratinocyte cultures exposed to blue light (400-500 nm) with unexposed controls. Title/abstract and full-text screening were conducted in duplicate. Data and risk of bias were extracted by one reviewer. Light parameters were subsequently verified by a second reviewer, while uncertainties regarding cell culture parameters were discussed with the review team.

RESULTS

Of 7508 screened records, 226 underwent full-text review and 44 studies met the inclusion criteria. Extracted data included irradiation and culture parameters, and assays on reactive oxygen species, proliferation, apoptosis, and viability. Blue light induced biological responses ranging from adaptive redox signaling to oxidative stress, reduced metabolic activity, and apoptosis. Shorter wavelengths exhibited a narrower margin between adaptive and cytotoxic responses, whereas prolonged exposure increased apoptotic activity. Heterogeneity dominated irradiation and culture parameters and all studies were classified with moderate or high risk of bias.

CONCLUSIONS

Blue light photobiomodulation elicits parameter-dependent keratinocyte responses indicating that biological effects are determined by irradiation conditions rather than wavelength alone. This review demonstrates diverse cellular responses to blue light but highlights an ill-defined window of effect.