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BackgroundFor herpes zoster (HZ) infection, early diagnosis and treatment are important in order to shorten the course of the disease and reduce sequelae, however, there is a lack of non-invasive diagnostic methods. Reflectance confocal microscopy (RCM) is a non-invasive technique often used to diagnose dyspigmented dermatosis, skin tumours, human papillomavirus infectious dermatosis, etc.ObjectivesTo evaluate the clinical value of RCM for the early diagnosis of HZ.Materials & MethodsWe collected RCM images from 30 HZ patients with typical vesicles in order to analyse their features. We then utilized RCM to analyse early lesions of another 12 HZ patients, who presented with localized erythema or papules, but not typical vesicles. In addition, we recruited one patient with HZ and observed the lesions over 14 days also using RCM.ResultsRCM images showed that the typical lesions of HZ mainly involved oedema of the spinous layer, intraepidermal blister formation, ballooning multinucleated giant (BMG) cells, and dermal papillary oedema. Among them, BMG cells were of specific diagnostic value. Early lesions of HZ patients without typical vesicles showed BMG cells under RCM. A few BMG cells were observed during the early stage of HZ. However, the number of BMG cells increased significantly as typical clustered blisters gradually appeared in the lesions. With the regression of the lesions, the number of BMG cells decreased gradually.ConclusionRCM, with the advantages of being non-invasive, rapid, and convenient, has an important role in monitoring the evolution of HZ.