Is Ozone Therapy Legal? The FDA "Toxic Gas" Statement, Explained

"Ozone is a toxic gas with no known useful medical application" comes from an FDA rule, 21 CFR 801.415, that sets limits for devices that release ozone into the air. The "toxic" part refers to breathing ozone, which really is harmful. The rule doesn't ban ozone therapy, and it has hardly changed since the 1970s [1][2].

Is ozone therapy legal? In the US, yes: no federal law bans ozone therapy. It is not FDA approved for any condition, and licensed clinicians use it under their own licenses and state rules. The FDA "toxic gas" sentence is about breathing ozone and about devices that release ozone into the air [1][3].

That one sentence gets quoted more than anything else about ozone therapy. Here's what it says in full, what it covers, where it's right, and where we think it's out of date. When we give our opinion rather than a documented fact, we say so.

This page is education, not legal advice.

What exactly does the FDA rule say?

The section is titled "Maximum acceptable level of ozone." Paragraph (a) reads, in full [1]:

"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."

Paragraph (b) gives the reason. It mentions other reported effects, but the main one is about breathing [1]:

"Although undesirable physiological effects on the central nervous system, heart, and vision have been reported, the predominant physiological effect of ozone is primary irritation of the mucous membranes. Inhalation of ozone can cause sufficient irritation to the lungs to result in pulmonary edema. The onset of pulmonary edema is usually delayed for some hours after exposure; thus, symptomatic response is not a reliable warning of exposure to toxic concentrations of ozone. Since olfactory fatigue develops readily, the odor of ozone is not a reliable index of atmospheric ozone concentration."

What is the rule actually about?

It's a device rule. It sits in the FDA's labeling regulations and tells makers and sellers of ozone-generating devices what they can release and how they can market them. A device is treated as "adulterated and/or misbranded" if, for example, it pushes ozone in an occupied room above 0.05 parts per million, releases ozone in hospitals, or is used "in any medical condition for which there is no proof of safety and effectiveness" [1].

It says nothing about whether a licensed clinician may use ozone. Federal law leaves the practice of medicine to the states: the FDA regulates products, and state boards regulate practitioners [3].

Is the "toxic gas" part right?

For breathing it, yes. Ozone irritates and inflames the airways, and the lungs have very little of the antioxidant protection that blood has. This is one point where the FDA and ozone therapy practitioners agree. The International Scientific Committee of Ozone Therapy (ISCO3) says the inhalation route is "absolutely prohibited" [4]. No ozone therapy method involves breathing the gas.

The same gas behaves very differently in blood and other body fluids, where antioxidants react with a small dose right away. That's the basis of ozone therapy, explained in how ozone therapy works.

What about "no known useful medical application"?

This is the part people argue about. Ozone therapy as practiced puts ozone into blood drawn from the body, into the rectum, ear or joints, or into oils and water. Whether those uses help is a research question, and the research has grown a great deal since the rule was written. Some trials show clear benefits, such as a double-blind trial in which 61% of people with a herniated lumbar disc became pain-free after ozone injections versus 33% after sham injections [6], and others are small or mixed. A 2026 umbrella review of seven meta-analyses, covering four uses (gum disease, COVID-19, diabetic foot ulcers and wisdom tooth surgery), rated the certainty of the evidence as low or very low and called for larger, better-designed trials [5]. You can follow new studies in our News & Research section.

Either way, a sentence written in the 1970s can't settle it.

Has the FDA statement ever been updated?

Not that we can find. The current wording matches the text the FDA published on February 13, 1976, when it reorganized its device rules and renumbered the old section 21 CFR 3.96 as 801.415 [2]. The section hasn't been amended since [1]. That means it predates almost all of the published ozone therapy research.

Our view: the breathing warning is sound and should stay. The "no known useful medical application" line is different. As we read the history, it was added to keep ozone therapy outside the regulatory system and discourage its use, rather than to study and regulate it, and it hasn't been revisited in 50 years of research. That's our opinion. The documented facts are the wording, the date, and that the FDA hasn't approved ozone therapy for any condition.

Does this make ozone therapy illegal?

No federal law bans ozone therapy. It isn't FDA approved for any condition, and no device has been FDA cleared for giving ozone to people. Licensed clinicians in the US use it under their own licenses, and state rules differ [3]. If you're a practitioner, check with your state board.

So why do people say ozone therapy is illegal? Usually because of the FDA sentence above, or because "not FDA approved" gets read as "banned". Those are different things: many treatments doctors use every day are not FDA approved for that use.

Practitioners who want to add ozone to a practice can start with our free IV Ozone 101 training.

Is ozone therapy legal outside the US?

Ozone therapy is used in clinics and hospitals across much of Europe, in Cuba and Russia, and in many other countries, and the rules differ by country and sometimes by region. The Madrid Declaration on Ozone Therapy, a consensus of ozone therapy associations from many countries, sets out the doses and methods those practitioners follow [4]. Ozone generators sold in the EU carry a CE mark, which shows the device meets EU safety and manufacturing standards; it is not an approval of ozone therapy for any disease.

What this means for you

• Never breathe ozone gas. Use ozone only with equipment and a method that keep it out of your lungs, in a ventilated room.
• Use measured doses. Ozone is dosed in micrograms per milliliter. See how to calculate a dose.
• Know the safety basics before you start: the safety of ozone therapy.
• Talk to a qualified practitioner if you have a health condition or take medication.

Common questions

Is ozone therapy legal?

In the US, no federal law bans it. It isn’t FDA approved, and licensed clinicians use it under their own licenses and state rules [3].

Why is ozone therapy illegal?

It isn’t. People often read "not FDA approved" or the FDA "toxic gas" sentence as a ban, but the rule is about breathing ozone and about devices that release it into the air [1].

Is ozone therapy FDA approved?

No. The FDA hasn't approved ozone therapy for any condition.

Why does the FDA call ozone toxic?

Because breathing it irritates and can damage the lungs. The rule's own explanation is about inhalation [1].

When was the statement written?

The current text dates back to at least February 1976, when the FDA renumbered it as 21 CFR 801.415. It hasn't been amended since [1][2].

Sources

1. 21 CFR 801.415, Maximum acceptable level of ozone. eCFR
2. Federal Register, Vol. 41, No. 31, February 13, 1976, p. 6896 (recodification of 21 CFR 3.96 as 801.415). govinfo.gov
3. 21 U.S.C. 396, Practice of medicine. Cornell LII
4. ISCO3. Madrid Declaration on Ozone Therapy, 3rd edition, 2020. isco3.org
5. Cacciatore S, et al. Effectiveness and Safety of Ozone Therapy in Humans: An Umbrella Review. Medical Sciences. 2026;14(2):289. doi:10.3390/medsci14020289
6. Paoloni M, et al. Intramuscular oxygen-ozone therapy in the treatment of acute back pain with lumbar disc herniation: a multicenter, randomized, double-blind, clinical trial of active and simulated lumbar paravertebral injection. Spine. 2009;34(13):1337-44. doi:10.1097/BRS.0b013e3181a3c18d