I’d like like to answer your question from a medical/scientific point of view and from the Reiki experience perspective.
Reiki is a natural Japanese wellness method for body and mind that involves a light touch. As a medical doctor, I can tell you that from a medical perspective, there should be no healing effects (other than relaxation, perhaps) from any method that involves hands-on healing; however, I have observed Reiki in action for well over a decade now, and I have no doubt in my mind about its positive effects on healing.
Technically and legally speaking, we should probably refrain from using the word “healing”, since it implies scientific/medical evidence of effectiveness of a licensed clinical treatment modality, which Reiki is not. It is neither scientifically proven, nor it is a licensed healing profession. I would like to add however, that although currently, there is no scientific proof that Reiki heals anything, I am certain that it is only a matter of time before we will learn otherwise.
From my observation of Reiki as a medical scientist, I can tell you that people receiving Reiki report improvements in physical symptoms, reduction in emotional suffering, and they also often share that they gain clarity or have a healing spiritual experience, not to mention feeling more relaxed and better overall with Reiki. I would say that probably about 50% of people receiving Reiki say that it felt “amazing”. I personally see Reiki as a mind-body-and-soul healing art, and in my experience, not only it can be very helpful for healing on multiple levels, but it appears to be beneficial significantly beyond the placebo effect.