Safety
Hyperbaric Oxygen Therapy Side Effects: What to Expect, What's Common, What's Rare
The most common side effects of hyperbaric oxygen therapy are ear or sinus pressure, temporary nearsightedness after many sessions, and mild fatigue. Serious effects, such as an oxygen-toxicity seizure or lung injury, are rare. Physician screening before treatment is how the rare ones are kept rare.
At a Glance
The Short Answer: Common, Uncommon and Rare
Hyperbaric oxygen therapy has a well-documented side-effect profile, and most of it is mild. A StatPearls review of hyperbaric complications cites an overall adverse-effect incidence of around 0.4% in one monoplace series. The table sorts the effects you may read about by how often they happen, using figures from that review.
| Group | Side effect | What the literature reports |
|---|---|---|
| Common and usually mild | Middle-ear barotrauma (ear pressure or pain) | The most common complication: at least 2% in monoplace series, and nearly 50% of all reported adverse events involved ear pain |
| Common and usually mild | Temporary nearsightedness | The most common effect on the eyes; improves after the course, usually within about six weeks, sometimes up to a year |
| Common and usually mild | Fatigue after a session | Commonly reported; typically passes within the day |
| Less common | Sinus pressure or pain | Usually sinus pain and swelling; more serious effects have been reported but are unusual |
| Less common | Confinement anxiety | About 25% of adverse-event reports; 8 per 10,000 treatments in one series |
| Less common | Tooth pain ("tooth squeeze") | Described as uncommon, but it can be painful |
| Rare and serious | Oxygen-toxicity seizure | About 1 per 5,000 to 10,000 treatments |
| Rare and serious | Pulmonary barotrauma, including collapsed lung | Rare, but the most serious form of barotrauma; the main reason lungs are screened |
| Linked to very long courses | Cataract formation | One study links new cataracts to about 150 or more daily treatments |
This article explains what can happen during and after treatment. For who should not have HBOT in the first place, see our safety and eligibility guide.
Most Common
Ear and Sinus Pressure (Barotrauma)
Why it happens
Your middle ear is a small air-filled space behind the eardrum, connected to the back of your throat by the Eustachian tube. When chamber pressure rises, the air in that space is squeezed into a smaller volume. If the tube opens and lets air in, pressure balances and you feel nothing more than a pop. If it stays closed, the eardrum is pulled inward. That causes fullness, then pain, and sometimes bruising or fluid behind the eardrum. Doctors call this middle-ear barotrauma. The sinuses work the same way, which is why congestion can cause facial pain.
How common it is
Middle-ear barotrauma is the most common complication of HBOT. StatPearls reports an incidence of at least 2% in monoplace series, and ear pain made up nearly half of all reported adverse events. Most cases are mild and settle with a pause in treatment.
Prevention and management
- Equalize early and often during pressurization, before your ears feel blocked.
- Speak up at the first sign of pain. Pressurization can be slowed or paused while you clear your ears.
- Tell us about colds and congestion before a session. Active upper respiratory infections raise the risk of ear and sinus injury, and a session may need to wait.
- Persistent trouble equalizing may call for equalization training or, for some people, small ear tubes placed by an ear specialist.
For step-by-step equalizing tips, see how to clear your ears and manage claustrophobia. Unfamiliar terms are explained in our glossary of barotrauma, oxygen toxicity and other terms.
Tooth squeeze
Occasionally, air trapped under a loose filling or in a tooth with decay can cause pain as pressure changes. StatPearls describes this dental barotrauma as uncommon but potentially quite painful. If you have dental work in progress, mention it at your assessment.
Your Eyes
Temporary Nearsightedness and Cataracts
Blurry distance vision during a course
Temporary nearsightedness, sometimes called hyperoxic myopia, is the most common effect of HBOT on the eyes. Repeated exposure to high oxygen levels changes how the lens of the eye bends light, so faraway objects can look slightly blurry. It builds gradually over many sessions rather than appearing after one. According to StatPearls, it is considered fully temporary once treatment stops: vision improves quickly within the first six weeks, though a return to your usual vision can take up to a year.
Two practical points follow. First, if your distance vision changes, tell the team so it can be noted. Second, ask your physician before buying new glasses during or just after a course, because your prescription is likely to shift back.
Cataracts
New cataracts are linked to very long exposures, far beyond a typical course. StatPearls notes one study suggesting new cataract formation starts after about 150 daily treatments, and another pointing to 300 to 850 hours of exposure. A typical outpatient course is 20 to 40 sessions. If a much longer course were ever being considered, this is one of the risks your physician would weigh.
After a Session
Fatigue and Hunger After Sessions
Feeling tired after a session is one of the most common things patients mention. Lying still for well over an hour, adjusting to pressure changes and breathing concentrated oxygen can all leave you ready for a rest. Some people also feel hungry afterward. These effects are usually short-lived and pass within the day.
- Eat and drink normally before and after your session unless your physician advises otherwise.
- If you feel drowsy, rest before you drive. Most people drive themselves home, and any restriction for you is discussed at your assessment. See can I drive myself home?
- Tell the team about any headache, ear pain or other symptom that is severe or keeps coming back.
For a picture of the whole visit, read what a session involves.
Rare but Serious
Oxygen Toxicity: Seizures and Lungs
Oxygen behaves like a medicine: the right dose helps, and too much for too long can cause harm. HBOT deliberately raises oxygen levels, so treatment plans are built to stay within limits.
Central nervous system toxicity
The most serious form is a seizure while breathing oxygen under pressure. It occurs about once every 5,000 to 10,000 treatments, according to StatPearls. Watching it happen is frightening, but StatPearls notes these seizures typically stop once the patient begins breathing normal air, with no other intervention needed.
Some things raise the risk, and they are part of screening for that reason:
- High fever
- A seizure disorder such as epilepsy
- The medication disulfiram, which blocks one of the body's defenses against oxygen damage
Many hyperbaric protocols include short periods of breathing air, often called air breaks, to lower the oxygen dose. Your physician sets the pressure and length of every session with oxygen limits in mind.
Pulmonary (lung) toxicity
Long or repeated oxygen exposure can irritate the airways. StatPearls describes symptoms ranging from a cough, to a burning feeling behind the breastbone, to shortness of breath. Tell the team if you notice any of these during a course, so your physician can review your plan.
Diabetes
Blood Sugar in People With Diabetes
Many people who receive HBOT have diabetes, often because of a diabetic foot ulcer. Low blood sugar during treatment is a recognized consideration for these patients, and published guidance from StatPearls describes managing it with point-of-care glucose monitoring.
What that means for you: if you have diabetes, tell the physician at your assessment how your diabetes is managed, including insulin and any glucose-lowering medicines. The team will explain your plan for treatment days before your first session. In general, do not skip meals before a session unless you have been told to, and let staff know right away if you feel shaky, sweaty or confused. See what a session involves for how a visit runs.
Feeling Enclosed
Confinement Anxiety
About 25% of adverse-event reports in the StatPearls review were classified as confinement anxiety, and one series recorded it in about 8 per 10,000 treatments. StatPearls notes it is not considered a true complication of the therapy, but it is real and worth planning for.
At our center you are treated in a single-person chamber that you can see out of, trained staff stay in communication with you throughout, and you can ask to stop at any point. If you are worried, tell us before your first visit. For practical strategies, read ear pressure and claustrophobia in HBOT.
Why We Screen
Rare Lung and Heart Events
Pulmonary barotrauma and collapsed lung
StatPearls calls pulmonary barotrauma the most severe type of barotrauma. If air is trapped in the chest, for example in someone with an untreated pneumothorax, it expands as pressure is released at the end of a session. That can turn into a tension pneumothorax, which can cause the circulation to collapse. It is rare, and it is the reason an untreated pneumothorax is the one absolute contraindication to HBOT. Lung conditions that trap air, such as some cases of COPD, asthma or lung bullae, also need careful review.
Heart conditions
Your heart health matters too. According to StatPearls, HBOT can be given safely when heart failure is appropriately managed, which is why your cardiac history is part of the assessment. For the full list of conditions that need evaluation, see who should not use a hyperbaric chamber.
The Bigger Picture
Are There Long-Term Side Effects?
For a typical course of 20 to 40 sessions, the main lasting concern people ask about is vision. Temporary nearsightedness improves after treatment ends, though it can take up to a year, and new cataracts have been linked to much longer exposures, around 150 or more daily treatments in one study.
What we do not have is strong data on people who do very long or repeated courses, such as healthy people using HBOT for general wellness. It is honest to say that the evidence there is limited. If you are reading about healthy volunteers doing dozens of sessions, keep in mind that those are research settings, not a proven standard of care.
At Generations Wellness
How Side-Effect Risks Are Reduced at Our Center
- A physician assessment first. Lungs, ears, medications, seizure history, devices and diabetes are reviewed under the direction of Dr. Rajwinder Singh Bahia, MD.
- A prescribed pressure and session length. You breathe medical-grade oxygen in a hard-shell monoplace chamber at the pressure your physician sets.
- Preparation before your first session. The team explains how to equalize your ears and how to prepare.
- Trained staff in communication with you for the entire session, and you can stop at any point.
- A check-in every visit. A cold, fever or new medication can mean a session is postponed.
Read more about how we prevent side effects through our standards, or weigh the whole picture in HBOT pros and cons.
Important
A physician assessment is required before beginning HBOT at Generations Wellness. HBOT complements, and never replaces, the treatment prescribed by your doctors.
Questions
HBOT Side Effects: Frequently Asked Questions
What are the most common side effects of HBOT?
Ear or sinus pressure during pressurization, temporary nearsightedness after many sessions, and mild fatigue afterward. Middle-ear barotrauma is the single most common complication.
Can you get oxygen toxicity from hyperbaric oxygen therapy?
Rarely. Oxygen-toxicity seizures occur in about 1 in 5,000 to 10,000 treatments and typically stop once normal air is breathed. Screening for fever, seizure disorders and certain medicines lowers the risk.
Does HBOT affect your vision?
It can cause temporary nearsightedness that builds over a course. Vision usually improves within about six weeks after treatment ends, though it can take up to a year.
Can HBOT cause cataracts?
New cataracts have been linked to very long exposures, around 150 or more daily treatments in one study. That is well beyond a typical 20 to 40 session course.
Why am I tired after hyperbaric oxygen therapy?
Resting still for a long session, pressure changes and breathing concentrated oxygen commonly leave people mildly tired. It usually passes within the day; rest before driving if you feel drowsy.
Is hyperbaric oxygen therapy safe?
It is an established medical treatment with a known, mostly mild side-effect profile when delivered with screening and physician oversight. It is not without risk, which is why an assessment comes first.
Sources
- StatPearls. Hyperbaric Complications. National Library of Medicine. ncbi.nlm.nih.gov
- Heyboer M, et al. Hyperbaric Oxygen Therapy: Side Effects Defined and Quantified. Advances in Wound Care, 2017. pmc.ncbi.nlm.nih.gov
- StatPearls. Hyperbaric Oxygen Therapy Contraindications. National Library of Medicine. ncbi.nlm.nih.gov
- StatPearls. Hyperbaric Contraindicated Chemotherapeutic Agents. National Library of Medicine. ncbi.nlm.nih.gov
- University of Iowa Health Care. Medical Risks of Hyperbaric Oxygen Therapy. uihc.org
- U.S. Food and Drug Administration. Hyperbaric Oxygen Therapy: Get the Facts. fda.gov
This page is educational and not medical advice. Frequency figures come from published reviews and do not predict your individual risk. A physician assessment is required before HBOT. See our full medical disclaimer.
Your Next Step
Begin With a Physician Assessment
Every course starts with an honest conversation and a physician assessment. No pressure, no obligation.
Prefer to talk? (369) 222-0979