Introduction: Melasma is a recurrent, symmetric, and chronic acquired hyperpimentation that presents gray-brown macules and patches with determined margins in areas exposed to light. There are many treatment options with different efficacies and side effects. In this study the therapeutic effect of 20% azelaic acid and 4% hydroquinone in treatment of melasma was assessed.

Methods: In this clinical trial, the study population consisted of all patients with clinical diagnosis of melasma, who referred to the outpatient clinic of dermatology of Hamadan, Farshchian Hospital from December 2013 to July 2014. A total of 44 patients were recruited. Patients were randomly divided to two groups and each group was treated with either azelaic acid or hydroquinone for four months. The MASI score was used to evaluate the improvement. P values of ≤ 0.05 were considered significant.

Results: Of 44 patients, 21 received 4% hydroquinone and 23 received 20% azelaic acid, with random allocation. Both groups were similar with respect to gender and age, and there were no significant differences between the two groups. The MASI score in both groups had a decreasing trend over time, and at the end of the fourth month, a significant difference was found between the two groups (P = 0.006). The overall mean MASI score in both groups had a significant difference at different times and during the entire trial period, mean MASI score of 20% azelaic acid was lower than 4% hydroquinone (P = 0.001).

Conclusion: Based on this study, we could conclude that 20% azelaic acid in comparison with 4% hydroquinone had better effects on treatment of melasma. Therefore, 20% azelaic acid is a good alternative for 4% hydroquinone in treatment of melasma.