I’ve recently run across some advertising for the wonders of ozone therapy in pets. This is a treatment that hasn’t caught on much in veterinary medicine (fortunately), but I thought I’d take a look at it before it becomes the next big fad.
What Is It?
According to the Food and Drug Administration (FDA),
Ozone is a toxic gas with no known useful medical application in specific, adjunctive, or preventive therapy. In order for ozone to be effective as a germicide, it must be present in a concentration far greater than that which can be safely tolerated by man and animals.
According to the Environmental Protection Agency (EPA),
ozone is an air pollutant that is harmful to breathe and it damages crops, trees and other vegetation. It is a main ingredient of urban smog.
Ordinary oxygen gas consists of two oxygen atoms bound together, hence its chemical name O2. Ozone contains three oxygen atoms (O3), and is very reactive, breaking down spontaneously and combining readily with other chemicals. These oxidation reactions are the reason ozone can be used as a disinfectant, killing microorganisms through production of oxidative free radicals.
Proponents of ozone therapy claim that it can be medically beneficial in several ways. Its ability to kill microorganisms and other living cells has been claimed to make it useful for treating infectious diseases and cancer. It is also thought by some to increase the amount of oxygen available to tissues, which may be useful in preventing or treating disease, and to stimulate or modify the immune system in a beneficial way.
Ozone is employed in medical applications in multiple ways, including direct injection into blood, muscle, joints, or body cavities, autohaemotherapy (removing blood from the patient, exposing it to ozone, and then returning the blood to the patient’s body), insufflation of the rectum, vagina, or other body spaces with ozone gas, administration of ozone treated water or saline, and topical application of ozone gas or ozone-treated substances.
Does It Work?
There are pre-clinical, in vitro, studies of ozone applied to infectious organisms and cancer cells and demonstrating it can kill these. As I have often pointed out, however, so can bleach, hydrochloric acid, and many other substances which are not appropriate to give to patients as a form of therapy. A few animal model studies have also suggested a benefit in cancer treatment.
Several reviews have found little controlled clinical research showing beneficial effects in patients treated with ozone therapy. Here are some of the conclusions from these reviews:
Ozone’s use in medicine has been debated for decades, but references to its use were sporadic in the major medical journals. Most of the claims of its efficacy were anecdotal…Current data on the usage of ozone therapy as therapeutic options for various health conditions lacks sufficient safety and therapeutic advantage over available conventional therapeutic modalities…There is insufficient clinical evidence to recommend ozone therapy as a form of alternative treatment….(Health Technology Assessment Report: Ozone Therapy, Ministry of Health, Malaysia, December, 2005)
Given the high risk of bias in the available studies and lack of consistency between different outcome measures, there is no reliable evidence that application of ozone gas to the surface of decayed teeth stops or reverses the decay process. There is a fundamental need for more evidence of appropriate rigour and quality before the use of ozone can be accepted into mainstream primary dental care or can be considered a viable alternative to current methods for the management and treatment of dental caries. (Cochrane Reviews. Ozone therapy for treatment of dental caries. 2004)
Oxygenation therapists proposed that disease is caused by absence of oxygen and loss of cellular ability to use oxygen for “good energy” metabolism, detoxification, and immune system function. Oxygen therapies are proposed in order to restore the body’s ability to produce “good” energy, to “detoxify” metabolic poisons, and to kill invading organisms. However, over the five decades that have passed since this concept was proposed, scientists have shown that:
- Anerobic energy metabolism (fermentation) is not the cause of cancer.
- Koch’s glyoxylide does not exist.
- Ingestion, infusion, or injection of hydrogen peroxide cannot re-oxygenate the tissues of the body.
- Ozone-treated blood infused during autohemotherapy does not kill AIDS virus in vivo. (Green, S. Oxygenation therapy: Unproven treatments for cancer and AIDS. Quackwatch.org)
Ozone therapy has been recommended to treat many conditions. There are numerous anecdotes about successful treatment with ozone therapy, although effectiveness and safety have not been proven scientifically. (Ozone Therapy, Intelihealth article, Natural Standard and Harvard Medical School, 2008)
“Hyperoxygenation” therapy–also called “oxymedicine,” “bio-oxidative therapy,” “oxidative therapy,” and “oxidology”–is a method of cancer management based on the erroneous concept that cancer is caused by oxygen deficiency and can be cured by exposing cancer cells to more oxygen than they can tolerate. The most highly touted “hyperoxygenating” agents are hydrogen peroxide, germanium sesquioxide, and ozone. Although these compounds have been the subject of legitimate research, there is little or no evidence that they are effective for the treatment of any serious disease, and each has demonstrated potential for harm. Therefore, the American Cancer Society recommends that individuals with cancer not seek treatment from individuals promoting any form of hyperoxygenation therapy as an “alternative” to proven medical modalities. (Questionable methods of cancer management: Hydrogen peroxide and other “hyperoxygenation” therapies. CA Cancer Journal for Clinicians. 2008;43(1):47-56.)
There is limited research in veterinary species. A lab animal study of rabbits suggested a benefit for cancer. A couple of recent studies in cows from a single research group in Croatia found a possible benefit of ozone in treating retained placentas and urovagina and in improving reproductive efficiency. An uncontrolled case series in dogs reported improvements in signs of intervertebral disk disease after ozone therapy (though often patients with this disease get better with rest or only supportive care anyway).
As is always the case, there are numerous positive anecdotes claiming dramatic success in treating a wide range of diseases, but for well-established reasons, we cannot rely on these stories as a demonstration that this treatment is safe or effective (c.f. here and here). And there are a few clinical studies suggesting a benefit, all with significant limitations. The balance of the evidence, however, does not support the efficacy of ozone therapy for any condition. Given the miraculous results claimed for this treatment, it would not be difficult at all to generate dramatic clinical trial evidence, so the absence of this evidence, despite decades of use, strongly suggest that the anecdotes and testimonials cannot be trusted.
The underlying theories used to justify the treatment are also dubious. As Dr. Green establishes in his article on Quackwatch, it is not plausible that low oxygen levels are responsible for many of the diseases ozone therapy is supposed to treat, and it is not likely that ozone therapy significantly increases the oxygen available to tissues in a patient that is treated with it. And while the hype about the benefits of antioxidants does not appear justified, it is certainly possible that free radicals and oxidative stress could actually cause health problems in patients treated with a potent oxidizing agent like ozone. Which leads to the question…
Is It Safe?
There are anecdotal reports in the media and in the scientific literature of adverse effects and even death following ozone therapy. Patients have died from gas bubbles in their bloodstream following injectable ozone treatment, and patients have suffered injury from the injection of ozone and from the apparatus used to instill ozone rectally, vaginally, and into body cavities. Accidental infection with HIV and hepatitis virus have also been reported from contamination during autohaemotherapy.
According to one scientific review, “The risks of ozone therapy are played down by its proponents. Yet, numerous reports of serious complications, including hepatitis, and at least five fatalities have been reported.”(Ernst E (2001). A primer of complementary and alternative medicine commonly used by cancer patients. Med J Aust, Jun 4; 174(11): 611-2)
The indirect risk of using ozone therapy, if it is ineffective, is that serious disease can progress and the opportunity to treat with truly effective therapies can be lost if one delays conventional therapy in favor of ozone therapy. The FDA referred to this risk, as well as the more direct hazards mentioned above, when reporting its decision in 2009 to seize equipment used for ozone therapy from a company illegally selling these unapproved medical devices. The FDA considers medical use of ozone as an unapproved drug, which makes such use subject to prosecution.
And as mentioned before, ozone has been intensively investigated as a pollutant, and there are many studies reporting harmful effects in humans and veterinary species.
The theoretical justifications for the medical use of ozone are weak and unproven. There are equally strong theoretical reasons why such use could be harmful.
Actually clinical research in humans is limited, but there is no consistent body of evidence to suggest ozone therapy is effective for any medical condition. There are anecdotal reports of injury, illness, and death caused by ozone therapy in humans.
The research is even more limited in veterinary species, and there is no consistent body of evidence to support the safety or effectiveness of ozone therapy for disease in dogs and cats.
Medical use of ozone is not approved in the U.S., and there have been prosecutions of individuals selling unapproved medical devices for use in ozone therapy.
Any use of ozone therapy in dogs and cats must be considered experimental and should only be conducted in the context of properly controlled, monitored, and approved clinical research trials. As with all unproven therapies, those selling ozone therapy will claim benefits and deny the risks. But in the absence of reliable information about the effects of ozone treatment, the chances of harming your pet are at least as good as the chances of helping them.