The efficacy and safety of trichloroacetic acid in the treatment of solar lentigo: a systematic review and meta-analysis

Solar lentigo is a common benign pigmented skin lesion from chronic sun exposure, particularly in aging populations. Various treatment modalities, including chemical peels, cryotherapy, and laser therapy, have improved its appearance. Trichloroacetic acid (TCA) is widely used for its exfoliative and pigment-reducing effects, but its efficacy and safety compared to other treatment options remain unclear. This systematic review and meta-analysis aim to evaluate the efficacy and safety of TCA in treating solar lentigo. While some included studies compare TCA with alternative treatment modalities, others focus solely on TCA outcomes. A systematic review was conducted following PRISMA guidelines. Studies assessing the use of TCA for solar lentigo treatment were identified from multiple databases. Data on study design, patient demographics, intervention characteristics—including TCA strength, number of treatments, and downtime between sessions—and treatment outcomes were extracted. A meta-analysis was performed to estimate the pooled prevalence of clinical improvement, complete lesion clearance, and adverse events associated with TCA treatment. Heterogeneity among studies was assessed using the I² statistic. A total of 13 studies were included, comprising various study designs with follow-up durations ranging from 4 to 26 weeks. The pooled prevalence of clinical improvement with TCA treatment was 80.8% (95% CI: 73.1–88.4, p < 0.001), indicating a high effectiveness rate. However, the prevalence of complete lesion clearance was 24.8% (95% CI: -5.4–55.0, p = 0.107), suggesting that while TCA significantly improves lesion appearance, total clearance is less frequent. The prevalence of adverse effects, including erythema and post-inflammatory hyperpigmentation, was 17.9% (95% CI: 4.1–31.6, p = 0.011). Efficacy and side effects appeared influenced by the TCA concentration, number of applications, and treatment intervals. TCA is an effective treatment option for solar lentigo, demonstrating a high rate of clinical improvement. However, complete lesion clearance remains limited, and adverse effects are notable, particularly in patients with darker skin tones. The variability in treatment outcomes observed across studies may be attributed to differences in treatment protocols, including TCA strength, number of treatments, skin phototypes, lesion locations, and practitioner experience. Standardized treatment protocols and further randomized controlled trials are needed to optimize efficacy while minimizing risks. Combination therapies may enhance outcomes and warrant further investigation.