How Does it work?
Current theories of how it works
1. Neurotransmitter 
Acupuncture affects the higher brain areas, stimulating the secretion of beta-endorphins and enkephalins in the brain and the spinal cord. The release of neurotransmitters influences the immune system and the antinociceptive system.
2. Autonomic Nervous System
Acupuncture stimulates the release of norepinephrine, acetylcholine and several types of opiates, affecting changes in their turnover rate, normalizng the automnomic nervous system and reducing pain.
3. Gate Control
Acupuncture activates non-nociceptive recesptors that inhibt the transmission of nociceptive signals in the dorsal horn "gating out" the painful stimuli.
4.Vascular-Interstital
Acupuncture manipulates the electrical system of the body by creating or enhancing closed-circuit transport in tissues. This faciclites healing by allowing the transfer of material and electrical energy between normal and injured tissues and cells.
5. Blood Chemistry
Acupuncture affects the blood concentrations of trigycerides, cholestrol and phospholipids, suggesting that acupuncture can both raise and diminsh peripheral blood compnents thereby regulating the body toward homeostasis.
The NIH consensus also suggests that acupuncture "may activate the hypothalamus and the pituitary gland, resulting in a broad spectrum of systemic effects. Alteration in the secretion of neurotransmitters and neurohormones and changes in the regulation of blood flow, both centrally and peripherally, it has been documented that there is also evidence of alternations in immune functions by acupuncture."