Postoperative risk assessment of post-inflammatory hyperpigmentation and the efficacy of delayed prevention following 532 nm Q-switched Nd:YAG laser treatment of solar lentigines: a randomized controlled study.

BACKGROUND Although post-inflammatory hyperpigmentation (PIH) is a common adverse event following laser procedures, studies evaluating its risk remain limited. OBJECTIVE To analyze PIH risk after 532 nm Q-switched Nd:YAG laser (QSNYL) treatment for solar lentigines and examine the efficacy of triple combination cream (TCC) for its prevention. METHODS In this single center, investigator-blinded, randomized controlled study, participants with solar lentigo either received TCC or emollient from 2 weeks post-QSNYL treatment. The occurrence of PIH was determined by three independent and blinded dermatologists. In vivo skin measurements and sun exposure questionnaires were examined to evaluate the risk of PIH. RESULTS A total of 28 patients with 67 solar lentigines were included in the analysis. In the control group, PIH occurred in 55.3% of the lesions. Risk factors for the occurrence of PIH were the increased erythema at weeks 2 (OR, 1.32; p = 0.035) and outdoor activity during 1-5 pm (OR, 8.10; p = 0.038). Treatment with TCC from 2 weeks post-QSNYL treatment significantly decreased the incidence of PIH (31.0% vs. 55.3%, p = 0.048). CONCLUSION Post-laser erythema and outdoor activity at the daytime are prognostic factors for the occurrence of PIH. Administering TCC could be considered for the prevention of PIH in high-risk patients.