1. ^*Department of Dermatology, Wake Forest University Medical Center, Winston Salem, North Carolina, USA
2. ^†Department of Neurobiology & Anatomy & Neuroscience Center, Wake Forest University Medical Center, Winston Salem, North Carolina, USA
3. ^‡Division of Dermatology, University of Massachusetts Medical School Worcester, Worcester, Massachusetts, USA

Correspondence: Gil Yosipovitch, MD, Associate Professor of Departments of Dermatology, Neurobiology and Anatomy, Wake Forest University Medical Center, Winston Salem, North Carolina 27157, USA. Email: gyosipov@wfubmc.edu

Received 12 December 2004; Revised 24 June 2005; Accepted 22 July 2005; Published online 15 November 2005.

Abstract

The aim of this study was to assess the effect of thermal stimuli or distal scratching on skin blood flow and histamine-induced itch in healthy volunteers. Twenty-one healthy volunteers participated in the study. Baseline measurements of skin blood flow were obtained on the flexor aspect of the forearm. These measurements were compared with skin blood flow after various stimuli: heating the skin, cooling the skin, noxious cold 2°C, noxious heat 49°C, and scratching via a brush with controlled pressure. Afterwards histamine iontophoresis was performed and skin blood flow and itch intensity were measured immediately after the above-mentioned stimuli. Scratching reduced mean histamine-induced skin blood flow and itch intensity. Noxious heat pain increased basal skin blood flow but reduced histamine-induced maximal skin blood flow and itch intensity. Cold pain and cooling reduced itch intensity, but neither affected histamine-induced skin blood flow. Sub-noxious warming the skin did not affect the skin blood flow or itch intensity. These findings suggest that heat pain and scratching may inhibit itch through a neurogenic mechanism that also affects skin blood flow.