The short answer
Ozone therapy involves exposing the body or blood to ozone gas and is marketed as an alternative cancer treatment. There is no reliable evidence that it cures or treats cancer, and the FDA warns ozone is a toxic gas with no proven medical use. Using it instead of proven treatment can be dangerous.
Ozone therapy exposes the body or blood to ozone gas.
There is no reliable evidence it cures or treats cancer.
The FDA warns ozone is a toxic gas with no proven medical use.
Using it instead of proven treatment can be dangerous.
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The claim
Ozone therapy means putting ozone gas into the body. Sometimes blood is drawn, treated with ozone, and returned. Other routes are used too. Some clinics and websites promote it as a natural way to treat or cure cancer. The pitch usually rests on the idea that cancer cannot survive in an oxygen-rich, 'ozonated' body.
What the evidence shows
Ozone therapy is not an approved cancer treatment, and there is no solid evidence that it treats or cures cancer. The National Cancer Institute makes the general point plainly. For many alternative therapies, we do not know how safe they are or how well they work, and some can get in the way of standard treatment. The 'cancer hates oxygen' idea has not turned into an effective therapy.
Why caution matters
Ozone is not just unproven. It can be harmful. In its own labeling rules, the U.S. Food and Drug Administration states that ozone is a toxic gas with no known useful medical application in specific, adjunctive, or preventive therapy. It adds that inhaling it can irritate the lungs enough to cause fluid build-up. The FDA has also taken reports from people who used ozone devices at home and then had asthma attacks, headaches and breathlessness. The FDA says no ozone device has been cleared or approved for cleaning CPAP machines.
The bottom line
On current evidence, ozone therapy is not a proven cancer treatment, and it can harm the lungs. The greatest danger is using it in place of treatment that works, or letting it delay that treatment. One large study found that people with early breast, lung or bowel cancer who chose alternative therapy instead of standard care were far more likely to die within five years. If you are thinking about any complementary approach, talk it over with your cancer care team first.
When to get help sooner
- Call 911 or go to an emergency department if you have chest pain or chest tightness, trouble breathing, coughing up blood, sudden severe shortness of breath, or you faint after ozone exposure or an infusion. Do not drive yourself.
- Call your care team right away if you have a temperature of 100.4°F (38°C) or higher, or redness, swelling or pus where a needle or line went in. These can be signs of infection.
- Call your care team within a day or two if you have a new cough or wheeze after ozone treatment that is not getting worse, or if you have delayed any part of your cancer treatment to try it.
Sources
- National Cancer Institute — Complementary and Alternative Medicine (CAM) for Patients
- 21 CFR 801.415 — Maximum acceptable level of ozone (eCFR)
- U.S. Food and Drug Administration — Do You Need a Device That Claims to Clean a CPAP Machine? (ozone and UV products)
- National Cancer Institute — Use of Alternative Medicine for Cancer and Its Impact on Survival

Common questions
Does ozone therapy cure cancer?
There is no reliable evidence that it cures or treats cancer, and it is not an approved cancer treatment.
Is ozone therapy safe?
The FDA warns ozone is a toxic gas with no proven medical use; inhaling it can irritate the lungs enough to cause fluid build-up.
Why do people believe it works?
It rests on a 'cancer cannot survive with enough oxygen' idea that sounds plausible but does not translate into an effective therapy.
What is the main danger?
Using ozone therapy instead of, or to delay, proven treatment — that is where the greatest harm lies.
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Sources last checked: 2026-08-13 what this meansLast updated: 2026-09-29Next planned review: 2027-01-13
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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