It has been proven to have beneficial effects in the treatment of certain problems (mainly pain management, but also other diverse uses i.e. while inducing labor). German insurance companies, who are rather strict with what they cover (almost always EBM), do cover acupuncture in a few limited areas (headaches are not included for instance). Through scientific testing and analysis it has been shown that hitting certain points from the TCM method (not nearly all ~400) cause relatively predictable physiological results. Anyhow, I figure if you stab a nerve with a small needle some effect will probably occur. There are also contraindications and unwanted side effects.
The hands and feet have evolved to have many highly sensitive nerve endings/receptors responsible for all of the sensations involved with touch. I am sure if you would put a needle into someones lip you may have a similarly strong reaction due to the density of receptors there as well. However, the lips are also more sensitive to pain, so the reaction would probably be less therapeutic. Not a fan of the use of 'action potential' in that manner either lol.
