Physiological Effects of Acupuncture remain unclear although changes following treatment are readily discerned, and can be measured biochemically, microscopically, and more recently by magnetic resonance imaging (MRI).

The initial pain-relieving response to acupuncture is transient, and has been associated with the release of neuro-transmitters. These chemical substances have a direct effect on the brain, dulling perception of pain. It is also thought that inhibition of nerve impulses occurs in the body, which blocks pain sensation from being transmitted centrally to the brain.

The pain-relieving effect of acupuncture is not just due to masking of symptoms. With ongoing acupuncture, a step-wise improvement in all aspects of the disease occurs. In psoriasis, initial reduction in skin irritation is seen, followed by a decrease in skin irritation. A gradual reduction in skin desquamation occurs later. These changes are progressive and reflect the underlying healing process.

Healing can be unexpectedly rapid in the treatment of acute infective processes e.g. skin sepsis (cellulitis), mastitis and tonsillitis. Pain-relief is rapid in most situations and is associated with a decrease in warmth and swelling, which continue abating in the ensuing 24 hours. Resolution of acute infections often occurs rapidly, over several days.

Changes in white cell numbers and other markers of immune activity have been documented following acupuncture, and this therapy has been used for treating both viral and bacterial infections because of its immune-stimulatory effects. It has also been reported to be useful in treating aplastic anaemia, a condition characterised by a reduction in red and white blood cells as well as platelets.

Studies on the treatment of depression with acupuncture using magnetic resonance imaging (MRI) techniques demonstrate a positive response to therapy associated with an increase in circulation to specific areas of the brain.