Intense capsaicin-induced C-fiber stimulation results in reversible lysis of the nerve soma, thereby making capsaicin wound instillation of potential interest for the treatment of post-operative pain. Clinical histological and short-term sensory studies suggest that the C-fiber function is partly re-established after skin injection of capsaicin. However, no study has evaluated the long-term effects of wound instillation of purified capsaicin on sensory functions. Patients included in a double-blind placebo-controlled randomized study of the analgesic effect of capsaicin after groin hernia repair were examined by quantitative sensory testing before, 1 week and 2 years post-operatively. The primary endpoint was occurrence of hyperalgesia/allodynia. The secondary endpoints were acute and late...