Here is the way low dose naltrexone works-- and it gives us a clue as to exactly why acupuncture, reiki, and even sham acupuncture can work.
http://en.wikipedia.org/wiki/Low_dose_naltrexoneBeta-endorphins are important regulators of the immune system. Naltrexone, which is a pure antagonist to opiates, causes an artificial blockade of the endorphin/opioid receptors in the brain. However, unlike the normal (~50 mg) dose of naltrexone used to treat drug addiction, which maintains this blockade continuously for 24 hours (preventing any derived pleasure from taking the forbidden drugs), low dose naltrexone (~3 mg to 4.5 mg) blocks the endorphin receptors for only a couple of hours. During that time, endorphins fail to attach to the receptors and the body compensates by creating more endorphins. (Note that Dr. Bihari prescribes LDN to be taken at bedtime to take advantage of the body's pre-dawn boost in endorphin production.) Once the low dose naltrexone dose has been metabolized, the body is left with a "normal" amount of endorphins as compared to healthy controls, which consequently "normalizes" the immune function. The link between endorphins and immune system regulation is a good candidate for more research.
There have been studies showing that acupuncture increases endorphins. The same is true for reiki.
If increasing endorphins can stop the progression of cancer and autoimmune disease, as theorized by the MDs who use LDN, then it certainly applies to acupuncture and reiki.
The so-called skeptics are overall dismissive of acupuncture, but admit that it can help pain due to the demonstrated ability of acupuncture to increase endorphins. Apparently, though, endorphins affect much, much more than mood, and pain, but have a direct and profound effect on the immune system.