The effect of hypnotically induced analgesia on flare reaction of the cutaneous histamine prick test.

The effect of psychological pain reduction on the cutaneous inflammatory process was investigated by studying the effect of hypnotically induced analgesia on the flare reaction of cutaneous histamine prick tests. Ten highly hypnotically susceptible volunteers had their cutaneous reactivity against histamine prick tests on both arms measured before hypnosis. Their pain-related brain potentials were measured on the basis of eight argon laser stimulations. These measurements were repeated in the hypnotic condition, where subjects were given repeated suggestions of analgesia in one arm. Final measurements were performed in the post-hypnotic condition. Subjectively felt pain was measured on a visual analogue scale. Results showed a mean reduction in subjectively felt pain of 71.7% compared to the baseline condition. A significant (P less than 0.01) mean reduction of the evoked potentials was found in the hypnotic analgesic condition compared to both the pre-hypnotic (49.9%) and the post-hypnotic condition (36.9%). A significant difference was measured in the histamine flare area between the pre-hypnotic and the hypnotic analgesic condition (P = 0.01-0.02) and between the hypnotic analgesic and the post-hypnotic condition when compared with the control arm. The mean ratio of flare area between the analgesic arm and the control arm was 1.04 (SD, 0.16) in the pre-hypnotic condition, 0.78 (SD, 0.22) in the hypnotic analgesic condition, and 1.37 (SD, 0.49) in the post-hypnotic condition. The results support the hypothesis that higher cortical processes can be involved in the interaction of inflammatory and pain processes.