Hi!
Marks especially burns on legs can last very long. The longest lasting mark that I have seen was scratch marks (from mosquito bites) that lasted 3 years. The best results for topical treatment for burn is those that had been started right after the burn/scabs have healed. A good topical regime to prevent PIH from burns is topical hydroquinone/steroid.
I do recommend scar gel (kelocorte) sometimes. SUNBLOCK is essential to prevent PIH. If you have used your hydroquinone/arbutin topical for more than 2-3 months and the improvement is minimal, you will likely require laser treatment.
We recommend picosure laser toning for such marks/PIH on body. It will require approximately 4-6 treatments to lighten/ remove the mark.
Best regards
Dr Yanni