Failure of acupuncture to produce localized analgesia.

The pain sensitivity of 49 healthy volunteers has been tested both before and during electro-acupuncture at two or three widely separated places on the body surface. Test areas fell into two categories. The "target" areas were within the part of the body that experienced acupuncturists predicted would be most affected by acupuncture of specified traditional points. "Non-target" control areas fell outside this zone of predicted maximal effect. The subjects and the observers who administered the tests knew that acupuncture anesthesia was being studied, but they did not know which areas were the "targets". Each subject was tested using at least two sensory testing methods. Altogether 4 different tests of pain sensitivity (pinprick discrimination, cold pain ratings, heat pain thresholds and pinch pain thresholds) were used. Small, but statistically highly significant, decreases in pain sensitivity occurred with all 4 tests during acupuncture. However, pain sensitivity fell by the same amount at "target" and "non-target" areas. The variability of the data was sufficiently low that moderate differences between areas would have been detected. The mechanism of "acupuncture anesthesia" is discussed in the light of these negative findings.