The ability of herpes zoster to develop into postherpetic neuralgia is a major concern for clinicians. Sympathetic nerves are extensively involved in the development and maintenance of pain, and skin temperature in the painful area may be increased or decreased, representing the degree of sympathetic versus parasympathetic involvement. Relationship between skin temperature differences and pain in patients with acute herpes zoster over a 6-month period as determined by infrared thermography BACKGROUND: Changes in skin temperature follow the regional distribution of acute herpes zoster, and infrared thermography is a non-invasive, ionizing ray-free diagnostic tool capable of providing information on normal and abnormal sympathetic and sensory nerve function. This study is about the feasibility of infrared thermography for predicting the development of acute herpes zoster into postherpetic neuralgia (PHN). METHODS: In 110 patients diagnosed with acute herpes zoster, infrared thermography was used to determine the temperature of the affected side and the temperature difference between the healthy and affected sides. Also, patients’ age, gender, time of skin damage onset and whether they developed PHN were recorded. temperature differences >0.6°C on the face and trunk were considered abnormal. RESULTS: The temperature was elevated in 35 patients compared to the healthy side, while it was decreased in 35 cases. The age of the patient and the duration of the disease affected the outcome of the treatment and were associated with the development of PHN. However, temperature difference between the healthy and the affected side did not significantly correlate with pain severity, disease duration, nociceptive hypersensitivity, or the development of PHN, p>0.05. CONCLUSION: Patient age and disease duration are the most important predictors of the development of acute herpes zoster into PHN, independent of the different changes in temperature. Infrared thermographic techniques were not used to predict whether herpes zoster could develop into PHN.