Abstract: Objective To evaluate the clinical efficacy of intradermal injection of methylene blue for treatment of moderate to severe acute thoracic herpes zoster and prevention of postherpetica neuralgia in elderly patients. Methods Sixty-four elderly patients with herpes zoster were randomized to receive a 10-day course of intradermal injection of methylene blue and lidocaine plus oral valaciclovir (group A, 32 cases) and intradermal injection of lidocaine plus oral valaciclovir (group B)． Herpes evaluation index, pain rating index, incidence of postherpetic neuralgia, and comprehensive therapeutic effect were compared between the two groups at 11, 30 and 60 days after the treatment. Results The baseline characteristics were comparable between the two groups (all P>0.05). Compared with that in group B, the time for no new blister formation, blister incrustation and decrustation, and pain relief was significantly shortened in group A (P<0.05) with also obviously lower pain intensity after the treatment. The incidence of postherpetic neuralgia was significantly lower in group A than in group B at 30 days (P<0.05), but not at 60 and 90 days after the treatment. The total clinical response rate was 93.8% in group A, much higher than that in group B (62.5%, P<0.05). Conclusion Intradermal injection of methylene blue can effectively shorten the disease course, reduce the pain intensity and prevent the development of postherpetic neuralgia in elderly patients with herpes zoster.