BACKGROUND: Herpetic disorders cause pain and skin lesion. So, asymmetric temperature of both sides of the involving dermatome has been reported in thermogram. This study examined the usefulness of infrared thermography for a predictor of post-herpetic neuralgia (PHN). METHODS: Patients with acute herpes zoster who underwent nerve block were randomly selected. Biographic data, including age, gender and times of onset of the skin lesions, development of PHN, combined diseases were recorded. Infrared thermography was performed and subjective pain severity, dysesthesia and allodynia, skin lesion size were assessed. RESULTS: The temperature differences between the lesion site and the contralateral site at lateral and posterior were significantly correlated with lesion size (P < 0.01) and the temperature differences at anterior and lateral site were correlated with duration of disease (ant: P < 0.01, lat: P < 0.05). The temperature differences were not correlated with the pain severity, dysesthesia and allodynia (P > 0.05). PHN was correlated with skin lesion size and infrared thermal imaging (P < 0.01). CONCLUSIONS: Infrared thermal imaging cannot demonstrate subjective pain objectively in herpes zoster. Short duration showed high temperature on the lesion sites compared to the contralateral sites. The patients with big skin lesions developed PHN more. The PHN can be predicted by the infrared thermal imaging as low temperature on the lesion site compared to the contralateral site.