Capsaicin-induced flare and vasodilatation in patients with post-herpetic neuralgia.

The aim of the present study was to investigate the role of primary afferent fibres with polymodal nociceptors in the various pain symptoms and signs associated with post-herpetic neuralgia (PHN). Forty-four patients with PHN affecting thoracic dermatomes were examined clinically for evidence of sensory disturbance to touch and pinprick and compared to 14 normal subjects and 9 subjects with evidence of past herpes zoster infection but no pain. The patients were then divided into 3 groups on the basis of their clinical symptoms and signs-those with steady burning discomfort only (n = 12), those with burning discomfort, allodynia and hyperalgesia to pinprick (n = 17), and those with burning discomfort, allodynia and hypalgesia to pinprick (n = 15).