Background: Cesarean section scars are post-surgical problems in women. Many active ingredients have been found to diminish scar formation. Clinical investigations on the onion extract have gained more attention due to its properties, such as improvement of scar appearance and texture. However, published studies evaluating the usefulness of the onion extract in the treatment of scars are controversial.

Methods: The three-month study period followed a prospective, randomized, and double-blinded design. Each enrolled subject's post-cesarean completely sealed wounds were divided into two halves along the closure axis. Each half was randomly assigned to the treatment with either silicone gel containing 5% onion extract or the silicone gel containing vitamin C. All subjects were respectively evaluated at the one, two, and three months of the treatment.

Results: After the three-month follow-up, there was a statistically significant difference in scar improvement between before and after treatment. None of statistically significant difference in the Patient and Observer Scar Assessment Scale (POSAS) and Vancouver Scar Scale (VSS) scores and melanin value was found between silicone gel containing 5% onion extract and the control silicone gel. However, the improvement of scar erythema by treatment with the silicone gel containing 5% onion extract was significantly greater than in the control group. No adverse effects were reported in either group.