The Therapeutic and Preventive Effects of Light‐Emitting Diode (<scp>LED</scp>) for Post‐Inflammatory Erythema and Hyperpigmentation: A Pilot Study

Background/Purpose Photobiomodulation (PBM) using light-emitting diodes (LEDs) benefits tissue regeneration and wound healing. However, evidence regarding the efficacy of LED for post-inflammatory erythema (PIE) and post-inflammatory hyperpigmentation (PIH) is limited. The aim of this study was to explore the effect of medical LED (830 nm and 590 nm) in the prevention and treatment of PIE and PIH. Methods The in vivo PIE/PIH model was simplified to erythema and pigmentation reaction after acute UVB exposure. 308 nm LED light (225 or 270 mJ/cm²) was induced in vivo in the PIE/PIH model on the thigh of ten healthy subjects. Every subject received therapeutic and preventive irradiation (n = 10 in each group). 830 nm (60 J/cm²) and 590 nm LEDs (20 J/cm²) were irradiated, respectively. For therapeutic irradiation, the PIE/PIH model was induced on D1, and LEDs were irradiated on D0, 1, 3, 6 and 8. For preventive irradiation, LEDs were irradiated on D0, 1, 3, 6, and 8 and the PIE/PIH model was induced on D9. Erythema index (EI), melanin index (MI), transdermal water loss (TEWL), and C-Cube photography were measured during 10-day follow-up visits. Results For therapeutic irradiation, ΔEI and ΔMI in the 830 nm treatment group were significantly lower than in the control group (ΔEI: 9.30 vs. 11.52, p = 0.027; ΔMI: 7.79 vs. 9.25, p = 0.026). No significant difference was found between the 590 nm treatment group and the control group in ΔEI or ∆MI (p > 0.05). For preventive irradiation, ΔEI in the 830 nm prevention group and the 590 nm prevention group were both significantly lower than the control group (830 nm: 9.85 vs. 19.90, p = 0.001; 590 nm: 12.50 vs. 19.90, p = 0.008). No significant difference was found between the two prevention LED groups (p > 0.05). Conclusions Both 830 nm and 590 nm LEDs showed preventive effects for PIE, and 830 nm LEDs could effectively improve PIE and PIH.