Camphor induces cold and warm sensations with increases in skin and muscle blood flow in human.

Application of camphor to the skin has been empirically thought to improve blood circulation. However, camphor's effects on blood circulation to the skin and on thermal sensation have not been well elucidated. In this study, we examined its effects on the quality of sensation as well as on skin and muscle blood flow in human. Nine adults (average age 37±9.4 years) participated in the study. Petroleum jelly containing 5%, 10%, 20% camphor, or 2% menthol was separately applied to the skin on the medial side of one forearm of each subject. Just after the application, camphor at each concentration induced a cold sensation in a dose-dependent manner. Within 10 min, each subject reported that the cold sensation had faded, after which it was replaced by a warm sensation. As reported previously, a cold sensation was induced by application of 2% menthol, but the subjects did not adapt to that sensation. In addition, menthol did not induce a warm sensation at all. Application of menthol has been shown to increase blood flow in the skin. Finally, we measured blood flow in skin and muscle after the application of camphor or menthol. Application of camphor or menthol separately induced increases in local blood flow in the skin and muscle. The present results indicate that camphor induces both cold and warm sensations and improves blood circulation.