Hyperbaric Oxygen Therapy (HBOT): How It Works, What It Treats, Side Effects, and What to Expect

Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review

Quick Answer: What is hyperbaric oxygen therapy?

Hyperbaric oxygen therapy (HBOT) is a treatment in which you breathe 100% oxygen inside a pressurized chamber at two to three times normal air pressure. The extra oxygen helps damaged tissue heal and fight infection. It is approved for conditions such as wounds, carbon monoxide poisoning and decompression sickness, and side effects are usually mild. [1]

What the research says

• HBOT speeds short-term healing of diabetic foot ulcers. A review of 12 randomized trials (577 participants) found that, in pooled data from 5 trials (205 people), ulcers were 2.35 times more likely to heal at six weeks with HBOT — but the benefit was not seen at one-year follow-up. (Kranke et al., Cochrane Database of Systematic Reviews, 2015) [2]

• HBOT lowered the risk of major amputation in hard-to-heal diabetic foot ulcers. A meta-analysis of 51 randomized trials (8 testing HBOT) found HBOT cut the odds of major amputation by about 72% (odds ratio 0.28) compared with standard care, although serious adverse events were more frequent. (Monami et al., Acta Diabetologica, 2025) [3]

• Among 12 diabetic foot ulcer treatments, HBOT was one of only two that reduced amputations. A network meta-analysis of 99 randomized trials (7,356 patients) found HBOT lowered amputation risk versus standard care (odds ratio 0.35), while stem cells and amniotic membrane therapy ranked higher for overall healing rate. (Hu et al., PeerJ, 2025) [4]

Key takeaways

• Hyperbaric oxygen therapy gives you 100% oxygen, compared with 21% in room air, under raised pressure. [1]

• It treats a defined list of approved conditions, from chronic wounds to carbon monoxide poisoning. [1]

• A session usually lasts one to two hours, and a full course can reach 30 or more sessions. [1]

• Most side effects are mild and temporary, such as ear pressure, sinus congestion and short-term nearsightedness. [1]

• It is not recommended during pregnancy or with a collapsed lung, fever, cold, or recent ear injury or surgery. [1]

Hyperbaric oxygen therapy at a glance

What is hyperbaric oxygen therapy?

Hyperbaric oxygen therapy is a medical treatment that delivers pure oxygen inside a pressurized chamber to treat chronic wounds and other conditions. [1]

Room air contains about 21% oxygen. During HBOT, you breathe air that is 100% oxygen. [1]

The chamber raises the pressure to two to three times higher than normal. That pressure helps your lungs take in and absorb far more oxygen than they could at normal pressure. [1]

Doctors use HBOT on its own or alongside other treatments, such as medicines or surgery. Depending on the chamber type, you sit or lie down during the procedure. [1]

How does hyperbaric oxygen therapy help the body heal?

Hyperbaric oxygen therapy helps the body heal by pushing more oxygen into the blood and on to injured tissue. [1]

Your tissues need enough oxygen to work properly. When they are injured, they need even more. [1]

The raised pressure helps your blood carry oxygen through the body, especially to damaged areas. This extra oxygen supports healing in three main ways: [1]

• Rebuilds tissue: it helps your body grow new skin, blood vessels and connective tissue.

• Fights infection: it helps your white blood cells protect the body from bacteria.

• Supports repair cells: it helps your body produce stem cells, which make other important cells such as blood, brain and muscle cells.

What conditions does hyperbaric oxygen therapy treat?

Hyperbaric oxygen therapy is approved to treat 13 conditions, ranging from diving injuries to severe infections and slow-healing wounds. [1][6]

People with chronic wounds tend to benefit the most. [1] Most research on HBOT for chronic wounds has studied foot ulcers in people with diabetes (see our guide to diabetic neuropathy). [2]

Which uses of hyperbaric oxygen therapy are not proven?

Hyperbaric oxygen therapy has not been proven safe and effective for many conditions that medical spas and alternative medicine centers advertise it for. [1]

These unproven claims include:

• Anti-aging (age-related symptoms or conditions)

• Autism spectrum disorder

• Cerebral palsy

• COVID-19

• Depression

• Hair loss (alopecia)

• HIV and AIDS

• Migraine headaches

• Sports injuries

• Strokes

There is not enough research and testing yet to show HBOT treats these conditions safely and effectively. [1]

Only have HBOT for an approved condition, from an experienced provider, in an accredited medical facility. Ask whether your provider holds certification in hyperbaric medicine. [1][7]

Who should not have hyperbaric oxygen therapy?

Hyperbaric oxygen therapy is not safe for everyone, and it can be dangerous if you have certain lung, ear or short-term illnesses. [1]

How do you prepare for hyperbaric oxygen therapy?

Preparing for hyperbaric oxygen therapy starts with a check of your condition, age and overall health, which helps your provider decide how long treatment should last and how many sessions you need. [1]

Before your first session:

• Share your medicines and implants. Some implanted devices, including pacemakers made in the 1960s, may malfunction under hyperbaric pressure. [1]

• Mention your skin care products. Pure oxygen can make some products ignite at lower temperatures. [1]

• Change into a hospital gown. Leave metal objects and electronic devices outside — they can spark and cause a fire in a high-oxygen space. [1]

• Bring only a small bottle of water. Nothing else is allowed inside the chamber. [1]

• Use the restroom first. Sessions usually run one to two hours. [1]

What happens during a hyperbaric oxygen therapy session?

During a hyperbaric oxygen therapy session, you sit or lie inside a special chamber while the pressure slowly rises and you breathe normally. [1]

There are two main chamber types:

When the door closes, you may hear a soft hiss as oxygen fills the chamber and the pressure builds. [1]

Your ears may feel clogged or start to pop, much like flying in a plane or driving through mountains. To ease it, yawn, or take a sip of water, hold your nose and swallow. [1] This ear pressure is a mild form of barotrauma.

A healthcare provider stays in the room the whole time to monitor you and answer questions. You may take short breaks to breathe normal air. [1]

What happens after hyperbaric oxygen therapy?

After hyperbaric oxygen therapy, your provider slowly lowers the chamber pressure so your body can adjust to normal pressure outside. [1]

Then your provider will:

• Help you out of the chamber or remove your mask or hood

• Check your blood pressure, pulse and ears

• Test your blood sugar if you have diabetes

Once you no longer need monitoring, you can change and go home. [1]

You may feel sleepy afterward. You do not need someone to drive you home, but it can be a good idea. [1]

How many hyperbaric oxygen therapy sessions do you need?

Most hyperbaric oxygen therapy courses run from once a week to five days a week, for up to 30 or more total sessions. [1]

Each session lasts about one to two hours. [1] The exact number depends on your condition and how your body responds.

Most people notice benefits after several sessions. Finishing the full course matters, and regular check-ins help your care team catch problems early. [1]

What are the side effects and risks of hyperbaric oxygen therapy?

Hyperbaric oxygen therapy is very safe when an experienced provider performs it, and most side effects are mild and temporary. [1][5]

Most people's distance vision returns fully to its usual level once treatment ends. [1]

Can you have hyperbaric oxygen therapy during pregnancy?

Hyperbaric oxygen therapy is not recommended during pregnancy because it can narrow the blood vessels in the placenta and lower oxygen levels in the baby's blood (fetal hypoxia). [1]

The one exception is carbon monoxide poisoning. A provider may recommend HBOT in that case, but only if the benefits outweigh the risks. [1]

Is there any recovery time after hyperbaric oxygen therapy?

There is no recovery time after hyperbaric oxygen therapy — you can return to your normal activities right after a session. [1]

When should you see a doctor about hyperbaric oxygen therapy?

See your doctor about hyperbaric oxygen therapy if you have a chronic wound or another condition that might benefit from it. Your doctor can help decide whether it is right for you. [1]

Seek help right away: if you develop breathing problems during or after HBOT, call your healthcare provider or go to the nearest emergency department immediately. [1]

Conclusion

Hyperbaric oxygen therapy is a relatively safe treatment that gives damaged tissue the extra oxygen it needs to heal and fight infection. It works best for approved conditions — especially chronic wounds — and most side effects pass quickly. [1]

The key is getting it from the right place, for the right reason. Ask your doctor whether your condition is on the approved list, choose an accredited facility, and complete the full course of sessions.

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FAQ

What is hyperbaric oxygen therapy used for?

Hyperbaric oxygen therapy is used for 13 approved conditions, including chronic wounds, burns, carbon monoxide poisoning, decompression sickness, gas gangrene, crush injuries and radiation injuries. It also treats severe anemia, some types of hearing and vision loss, and severe bone and skin infections.

How long does a hyperbaric oxygen therapy session last?

A hyperbaric oxygen therapy session usually lasts one to two hours. Sessions can be scheduled once a week up to five days a week, depending on your condition.

How many hyperbaric oxygen therapy sessions will I need?

Hyperbaric oxygen therapy courses can reach 30 or more total sessions. Your provider sets the number based on your condition, age and overall health, and most people notice benefits after several sessions.

Is hyperbaric oxygen therapy safe?

Hyperbaric oxygen therapy is very safe when an experienced provider performs it in an accredited facility. Most side effects, such as ear pressure and sinus congestion, are mild and temporary, while oxygen toxicity and seizures are rare.

Does hyperbaric oxygen therapy hurt?

Hyperbaric oxygen therapy is not usually painful, but your ears may feel clogged or pop as the pressure rises, much like on a plane. Yawning, or sipping water while holding your nose and swallowing, can relieve the pressure.

Who should not get hyperbaric oxygen therapy?

Hyperbaric oxygen therapy may be dangerous for people with a collapsed lung, lung diseases such as COPD, cystic fibrosis or emphysema, a fever or cold, or a recent ear injury or ear surgery. It is also not recommended during pregnancy.

Can hyperbaric oxygen therapy treat autism, stroke or aging?

Hyperbaric oxygen therapy has not been proven to safely and effectively treat autism, stroke, anti-aging, depression, migraines or several other conditions some centers advertise. Only use it for an approved condition from an experienced provider.

When should I get emergency help during hyperbaric oxygen therapy?

Get emergency help if you develop breathing problems during or after hyperbaric oxygen therapy. Call your healthcare provider or go to the nearest emergency department right away.

How can I ease ear pressure during hyperbaric oxygen therapy?

Ear pressure is common as the chamber pressure changes. Yawning, or sipping water while holding your nose and swallowing, can help; tell the staff if the pain does not ease.

What should I leave outside the hyperbaric chamber?

Leave metal objects and electronic devices outside, because they can spark and cause a fire in a high-oxygen space. The staff will tell you what to wear and which personal items are not allowed.

Related Reading

What Is Carbon Monoxide Poisoning? Symptoms, Causes and How It's Treated explains carbon monoxide poisoning symptoms and emergency treatment.

Gas Gangrene: Symptoms, Causes, Diagnosis, Treatment, and Outlook — What You Need to Know covers a serious tissue infection that needs urgent treatment.

Barotrauma: The Pressure Injury From Flying and Diving That's Usually Minor — but Can Turn Life-Threatening When It Hits Your Lungs or Gut explains pressure-related injury to the ears and sinuses.

Osteoradionecrosis: Symptoms, Causes, and Management Strategies explains bone damage after radiation therapy and how it is managed.

References

1. Cleveland Clinic. Hyperbaric Oxygen Therapy: What It Is & Benefits, Side Effects. Cleveland Clinic. Last updated January 7, 2023. https://my.clevelandclinic.org/health/treatments/17811-hyperbaric-oxygen-therapy

2. Kranke P, Bennett MH, Martyn-St James M, et al. Hyperbaric oxygen therapy for chronic wounds. Cochrane Database Syst Rev. 2015;2015(6):CD004123. PMID 26106870. https://doi.org/10.1002/14651858.CD004123.pub4

3. Monami M, Scatena A, Ragghianti B, et al. Effectiveness of most common adjuvant wound treatments (skin substitutes, negative pressure wound therapy, hyperbaric oxygen therapy, platelet-rich plasma/fibrin, and growth factors) for the management of hard-to-heal diabetic foot ulcers: a meta-analysis of randomized controlled trials for the development of the Italian Guidelines for the Treatment of Diabetic Foot Syndrome. Acta Diabetol. 2025;62(7):1081-1095. PMID 39724338. https://doi.org/10.1007/s00592-024-02426-7

4. Hu X, Meng H, Liang J, et al. Comparison of the efficacy of 12 interventions in the treatment of diabetic foot ulcers: a network meta-analysis. PeerJ. 2025;13:e19809. PMID 40821981. https://doi.org/10.7717/peerj.19809

5. Heyboer M 3rd, Sharma D, Santiago W, et al. Hyperbaric Oxygen Therapy: Side Effects Defined and Quantified. Adv Wound Care (New Rochelle). 2017;6(6):210-224. PMID 28616361. https://doi.org/10.1089/wound.2016.0718

6. U.S. Food and Drug Administration. Hyperbaric Oxygen Therapy: Get the Facts. FDA. Last updated July 26, 2021. https://web.archive.org/web/20251218065045/https://www.fda.gov/consumers/consumer-updates/hyperbaric-oxygen-therapy-get-facts

7. Undersea & Hyperbaric Medical Society. Indications for Hyperbaric Oxygen Therapy. UHMS. Accessed October 31, 2026. https://uhms.org/resources/featured-resources/hbo-indications.html

Medical disclaimer

This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Always talk to a qualified healthcare provider about your own health, and seek emergency care right away if you have trouble breathing or another urgent symptom.