Acupuncture derives from the concept in traditional Chinese medicine that disease results from a disruption in the flow of chi—the body's circulating life energy—and imbalances in the forces of yin and yang. Chi is said to flow along pathways in the human body known as meridians. According to Eastern thought, there are as many as 20 meridians and more than 2,000 acupuncture points found along them. Applying tiny needles—or, sometimes, pressure or heat—to those points is believed to deliver therapeutic effects for patients.
How acupuncture works is a still mystery Western researchers are still attempting to understand. In a consensus statement issued by the National Institutes of Health in 1997, scientists acknowledged that there is "clear evidence" that acupuncture works for treatment of postoperative and chemotherapy-induced nausea and vomiting. They also found evidence of pain relief from conditions such as postoperative dental pain, menstrual cramps, tennis elbow, and fibromyalgia. In other words, we don't know how it works, but it seems to.