As a Reiki Master/Teacher I believe that Reiki can be used on anyone and you will not be interferring in their Karmic Lesson or their freewill if stated like I do, that Reiki is only for their highest good if appropriate. This way if they have a karmic lesson to learn Reiki will not interfere with that lesson. If what ever ails them is part of a lesson they have to learn, then Reiki will not interfere with that either. If their lesson is over then Reiki can help them to either 1 of 2 things, 1-recover from their ailment, 2-help them to have a peaceful crossing over. My spouse had the AIDS Cancer KS, the doctor couldn't explain why he had it, according to what they all know his t-cells were high enough so he should not have had the cancer. They did chemo on him and I hesitated on doing Reiki out of fear of interfering with Karma for him if that was the case, or any lessons this may have been for, or if this was just meant to be. So I sent him Reiki if it was for his highest good and appropriate. The KS went away after a few months. Strange part of it was that his t-cells had dropped so low that the KS should have still been around. The doctor's are still confused, though his nurse and I both know what had happened. His nurse was a Reiki practitioner as well. In my faith, you can send healing energies of anykind to anyone in need and state as long as it's for their higher good, will not interfere with any karmic lessons or their freewill. The healing will either work, or it won't. We just use reiki or any other healing to channel the healing energies of our creator if it is allowed to happen, no more and no less. Just my thoughts and opinions of this.