The practice of reiki has been around for a long time, and by definition it has been here for as long as we can trace back life, it translates to "universal life force energy" rei being the life force we all share, and ki being energy.
The practice of reiki requires almost no experience or prior knowledge, it can be taught to and done by any one on any living thing, it cannot cause any sort of harm or negative side effect, and its benefits can be felt immediately in some cases.
To perform reiki, one must simply hold their hand in a "cupping" gesture, and hover their palm over the affected area that one wishes to treat. that is all.
For an added boost, one may employ almost ay other type of healing technique along with reiki, such as chanting, crystals, aromatherapy, light therapy, and much more. Try some out and take notes of your results with each attempt, to find what works best for you personally.
The hands are very potent chakras and the body is electromagnetic. if your intention to heal (which is a natural default of all creatures) can be channeled through your hand you can effectively heal almost any ailment. Reiki practice should never substitute professional medical attention when it is required, it can, however, serve to assist in the healing process.