Scientists have performed acupuncture on mice with sore paws to pinpoint how the ancient Chinese medical practice might alleviate pain in humans. After a half-hour session, the mice felt less discomfort in their paws because the needles triggered the release of a natural painkiller, say the researchers. The needles stimulated cells to produce adenosine, an anti-inflammatory and painkilling chemical, that was effective for up to an hour after the therapy was over. The discovery challenges a widely held view among scientists that any benefit patients feel after having acupuncture is purely due to the placebo effect. Traditional practitioners claim acupuncture works by improving the flow of “qi energy” along “meridians”, but the latest research, published in Nature Neuroscience, points to a less mystical explanation. Although this study explains how acupuncture can alleviate pain, it sheds no light on any of the other health benefits that some practitioners believe it can achieve.