We study 0.075% capsaicin lotion is safe, well tolerated and provide significant pain relief in patients with PDN compared with placebo lotion as a randomized, double- Blind, crossover, placebo-controlled trial for 20 weeks throughout the study in 42 participants. All participants are provided both 0.075% capsaicin lotion and placebo lotion. Each agent will be applied for 8 weeks then stop for 4 weeks, after that another agent will be used for 8 weeks. We keep following up all of them by calling and appointment to get information in effectiveness and adverse effect at 0,2,4,8,12,14,16,20 week, respectively.