Background: Melasma is a difficult-to-treat hyperpigmentary disorder. While cysteamine is a known potent depigmenting agent, its efficacy in treating melasma has not been tested.

Objectives: To study the efficacy of cysteamine 5% cream in the treatment of patients with epidermal melasma.

Methods: In this double-blind randomized study, participating patients (n = 50) received either placebo (n = 25) or cysteamine cream (n = 25). Cysteamine cream or placebo were applied on the lesions once a day at bedtime over 4 months. The efficacy of treatments was determined through Mexameter skin colorimetry, Melasma Area Severity Index (MASI) score, Investigator's Global Assessment (IGA) and patients' questionnaires, all performed at baseline and after 2 and 4 months of treatment.

Results: At baseline, the mean differences between pigmented and normal skin (calculated by Mexameter) were 75.2 ± 37 and 68.9 ± 31 in the cysteamine and placebo groups, respectively. After 2 and 4 months of application of cysteamine and placebo cream, the mean differences were 39.7 ± 16.6 and 26.2 ± 16 in the cysteamine group, and 63.8 ± 28.6 and 60.7 ± 27.3 in the placebo group, respectively. Statistically significant differences were found between the group outcomes at both points (P = 0.001 and P < 0.001). At the end of the treatment, the MASI scores were significantly lower in the cysteamine group vs. placebo (7.2 ± 5.5 vs. 11.6 ± 7.9, P = 0.02). The IGA and patients' viewpoints indicated significant efficacy of cysteamine cream vs. placebo.

Conclusions: Cysteamine cream showed significant efficacy in the treatment of melasma.