An article in the journal Mediators of Inflammation, “Anti-inflammatory actions of acupuncture”  outlines various ways one essential mechanism of acupuncture may stimulate the body’s inflammatory and anti-inflammatory activities.
Puncture by an acupuncture needle mobilizes the body’s own defenses, improves blood flow to organs, activates cell growth, and influences the movement of substances in and out of cells. Among the chemicals stimulated by the insertion of an acupuncture needle are neuropeptides such as calcitonine gene-related peptide (CGRP), which is a substance that both prevents and promotes some forms of inflammation. Another neuropeptide known as, Substance P, works in conjunction with CGRP to create edema and inflammation, both of which are important in containing an injury and bringing red and white blood cells and nutrition to the site of injury.
Acupuncture stimulates or otherwise influences the production of other substances involved in inflammation. Beta-endorphins, another group of neuropeptides, promote the analgesic (pain-reducing) effects of acupuncture. Cytokines, produced by white blood cells, “provide signals to regulate immunological aspects of cell growth and specific immune response” mostly local to their production but sometimes systemically.
 Nitric oxide (NO), used by the body to expand the size of blood vessels (vasodilatation), is another component of the inflammatory process that brings blood where it is needed. Acupuncture’s initial effect is thus to engage the body’s own defenses.
While “high levels of CGRP have been shown to be pro-inflammatory , . . . CGRP in low concentrations exerts potent anti-inflammatory actions . . . . Therefore, a well-performed and frequently applied ‘low-dose’ treatment of acupuncture could provoke a sustained release of CGRP with anti-inflammatory activity, without stimulation of pro-inflammatory cells.” This dual action, inflammatory and anti-inflammatory, may explain why acupuncture is effective in the short term for acute disorders and is also effective in the long term for chronic illness.
1. Anti-inflammatory actions of acupuncture. Mediators of Inflammation, 12(2), 59-69 (April 2003). Freek J. Zijlstra, Ineke van den Berg-de Lange,Frank J. P. M. Huygen1 and Jan Klein.
2. Tabor’s Medical Dictionary, 18th Edition.