In general, placebo effect is a human phenomenon. It is observed when a person perceives an improvement due to his or her expectation of positive effect of a specific treatment.
Every healing modality for humans has some degree of placebo effect. Placebo effect can range widely, from a few % up to about 30%, and the degree of placebo effect depends on multiple factors.
When it relates to humans, the real question is whether or not the specific treatment is more effective than a placebo. The only way to answer that question, is to conduct a placebo-controlled clinical trial, comparing a specific treatment for a specific problem to a placebo. A large number of people participating in the study is usually needed in order to determine whether or not the difference between the improvement in the placebo and the treatment group is statistically significant. If there is a statistically significant difference in a series of well-designed studies, then we can conclude that the effect of a specific treatment for a specific problem is real, and that it is not just due to a placebo effect. Until this extensive research is completed, we cannot make that determination.
Note, in my case, it was through decade-long observation of Reiki, Healing Touch and Acupuncture being effective for hundreds and hundreds of patients, that I could see that those modalities was effective significantly above 30%. It was only through that extensive observational evidence (and my neutrality towards the final answer) that I was able to come to a scientific conclusion that Alternative Medicine modalities such as Reiki, Healing Touch and Acupuncture can be effective beyond the placebo effect. With that said, it was my conclusion and my conclusion only, which has not been adequately tested by well-designed placebo-controlled clinical trials (at least in case of Reiki and Healing Touch). This means that although I am convinced that Reiki can be very helpful, and helpful beyond the placebo effect, it is by no means a scientific fact, since it has not yet been proven by scientific studies.
When it comes to animals, the placebo effect has not been adequately studied. I would expect, that those animals who can sense a caring human approach would be a subject to a placebo effect. It is not uncommon to see what's called a "caring nurse" phenomenon in human studies. This phenomenon is observed when the clinical research center staff is behaving in a caring way towards research participants, which significantly increases the placebo effect, often to the point, that it is impossible to demonstrate a statistically significant difference even between the treatment that is already known to be effective and placebo. I can imagine that with animals such as cats, dogs, horses, certain birds, etc., we can observe a similar phenomenon, where the effect of a caring healer would increase the degree of a placebo effect of an energy treatment. So just like with humans, the only way to scientifically demonstrate that a healing modality is more effective than a placebo for animals, is to conduct a series of well-designed studies, and specifically studies that take the "caring healer" phenomenon into account. There is no other way to answer that question.
On a different note, people don't utilize energy medicine for themselves or for their pets because it has been scientifically proven to work (it hasn't been), but because they have either heard good things about it or have already experienced it with positive results themselves. So whether or not it is a placebo effect, if what you do it works, it works. :)
Dr. Maria Danilychev, MD is a medical doctor (hospice medical director) and a Jikiden Reiki Shihan.