Reiki works in mystical and scientific ways

During the Reiki treatment the brain wave patterns of both giver and receiver become synchronized in the 7-8 Hz alpha state characteristic of deep relaxation and meditation; they pulse in unison with the Earth's magnetic field, the infinite energy source also known as the Schumann resonance. The pulsating biomagnetic field emitted from the hands focuses mainly in this alpha state and sweeps regularly from 0.3-30 Hz.

This range of frequency stimulates healing in the body, with specific frequencies being suitable for different tissues. Brain waves travel throughout the body and gather cumulative strength as they flow to the periphery, especially to the hands. During these moments the biomagnetic field of the practitioners' hands is at least a thousand times greater than normal. The effects are mirrored by the giver and receiver and both benefit from the treatment.

There are many other effects including emotional and hormonal ones that are much more difficult to measure scientifically. But all this supports the subjective experience of "oneness" and expanded consciousness elated by those who regularly practice Reiki.

A simple explanation of what Reiki is

Reiki is the name of a a health system that uses natural energy to heal. It's the same energy that brings us the 4 seasons. Our body has a natural healing ability visable to the human eye if you check how a cut on your finger heals. The body sends us signals when it needs attention usually a rash,a pain,
etc; How we respond is the key to good health. Being aware of the natural earth's energy we
can direct it to within ourselves to unblock trapped energy be it physical,emotional and spiritual.

Like acupuncture and other healing energy systems, many Reiki sessions may be needed to get to the root of say a migraine headache and other health problems.