An overview of Cochrane reviews found that acupuncture is not effective for a wide range of conditions, and they suggest it may be effective for only chemotherapy-induced nausea/vomiting, postoperative nausea/vomiting, and idiopathic headache.
In the 20th century, as it spread to the United States and Western countries, the spiritual elements of acupuncture that conflict with Western beliefs were abandoned in favor of tapping needles into nerves.
In TCM, the four diagnostic methods are: inspection, auscultation and olfaction, inquiring, and palpation.
Inspection focuses on the face and particularly on the tongue, including analysis of the tongue size, shape, tension, color and coating, and the absence or presence of teeth marks around the edge.
The most common mechanism of stimulation of acupuncture points employs penetration of the skin by thin metal needles, which are manipulated manually or the needle may be further stimulated by electrical stimulation (electroacupuncture).
Needles vary in length between 13 to 130 millimetres (0.51 to 5.12 in), with shorter needles used near the face and eyes, and longer needles in areas with thicker tissues; needle diameters vary from 0.16 mm (0.006 in) to 0.46 mm (0.018 in), with thicker needles used on more robust patients.
Thinner needles may be flexible and require tubes for insertion.