Because acupuncture needles penetrate the skin, many forms of acupuncture are invasive procedures, and therefore not without risk. However, injuries are rare among patients treated by trained practitioners. Forms of acupuncture such as the Japanese Tōyōhari and Shōnishin often use non-invasive techniques, in which specially-designed needles are rubbed or pressed against the skin. These methods are common in Japanese pediatric use.
Hematoma may result from accidental puncture of any circulatory structure. Nerve injury can result from the accidental puncture of any nerve. Brain damage or stroke is possible with very deep needling at the base of the skull. Also rare but possible is pneumothorax from deep needling into the lung, and kidney damage from deep needling in the low back. Needling over an occult sternal foramen (an undetectable hole in the breastbone which can occur in up to 10% of people) may result in a potentially fatal haemopericardium.
Certain acupuncture points have been shown to stimulate the production of adrenocorticotropic hormone (ACTH) and oxytocin; these points are contraindicated for use on pregnant women to avoid inducing abortion or harming the fetus.
Sometimes, when treating pain or using acupuncture as an anesthetic, a mild electrical current is applied to the needles. This stimulates the nerve cells in the area of the needles so that they become depleted of the chemicals needed to transmit signals. Prolonged stimulation of nerve cells in this way can cause irreversible damage.
The NIH consensus panel said: “Adverse side effects of acupuncture are extremely low and often lower than conventional treatments.
Needles that are not properly sterilized can transfer diseases such as HIV and hepatitis. Most acupuncturists in the USA use sterile one-time-use needles.