Taking safety seriously
Hyperbaric oxygen therapy is generally considered safe when administered properly in an appropriate facility. It has been used in medicine for decades, and serious complications are uncommon. But safe does not mean risk-free, and any honest discussion of HBOT must cover what can go wrong, who should not have the treatment, and what a responsible clinic does to minimize risk.
This guide covers side effects, contraindications, and safety practices in plain terms. If you are considering HBOT, this information helps you have an informed conversation with the clinic and your doctor.
The most common side effect: ear pressure
By far the most common issue with HBOT is discomfort in the ears during pressurization and depressurization. As chamber pressure changes, the pressure on either side of the eardrum must equalize. If it does not, you feel fullness, discomfort, or pain, similar to what some people experience during airplane descent but potentially more intense.
Most people learn to equalize without difficulty using simple techniques: swallowing, yawning, jaw movements, or the gentle Valsalva maneuver (pinching the nose and blowing softly). Clinic staff will coach you through this before your first session and will slow the pressurization rate if you need more time.
If equalization fails and pressure continues to build, the eardrum can be injured, a condition called middle ear barotrauma. This is the most common HBOT-related injury, but it is largely preventable with proper technique and attentive staff. Anyone with a current ear infection, significant congestion, or a history of ear surgery should discuss this with the clinic before treatment. In some cases, pressure-equalization tubes may be recommended before starting a course of HBOT.
Sinus and dental pressure
Similar pressure effects can occur in the sinuses. If your sinuses are congested from a cold or allergies, the pressure may not equalize properly, causing pain. Most clinics will postpone your session if you have significant congestion. This is routine and not a cause for concern.
Dental work can occasionally cause issues. Air trapped under a filling or around dental work can expand or contract with pressure changes, causing tooth pain. This is uncommon, but worth mentioning to the clinic if you have recent or extensive dental work.
Vision changes
Some patients notice temporary changes in vision during a course of HBOT, typically a slight shift toward nearsightedness. This effect is related to oxygen effects on the lens of the eye and usually reverses within weeks after treatment ends. It is more commonly reported with longer treatment courses at higher pressures.
There is also a rare but serious eye concern: prolonged HBOT at high pressures may contribute to cataract development in susceptible individuals, though this is associated with extended treatment courses rather than typical use. Anyone with significant eye conditions should discuss them during screening.
Oxygen toxicity
Breathing pure oxygen under pressure for extended periods can, in rare cases, cause oxygen toxicity. The most dramatic form is a seizure, which can occur if oxygen exposure exceeds safe limits. This is why HBOT protocols include air breaks, periods during the session when the patient breathes normal air to interrupt continuous oxygen exposure.
With proper protocols, oxygen toxicity seizures are rare. When they do occur, they typically resolve without lasting effects once the oxygen exposure is stopped. Reputable clinics follow established protocols that keep oxygen exposure within safe limits, and staff are trained to recognize and respond to any signs of toxicity.
Lung-related oxygen toxicity is a concern with very prolonged exposures, generally beyond what is used in standard HBOT protocols. Mild chest tightness or cough after sessions is occasionally reported and usually resolves quickly.
Who should not have HBOT
Certain conditions make HBOT unsafe, and a proper screening should identify them:
- Untreated pneumothorax (collapsed lung). This is an absolute contraindication. Pressure changes can convert a simple pneumothorax into a life-threatening tension pneumothorax. Anyone with a history of spontaneous pneumothorax needs careful evaluation.
- Certain lung conditions. Severe COPD with air trapping, particularly with blebs or bullae in the lungs, increases the risk of pulmonary barotrauma.
- Uncontrolled seizure disorders. Since oxygen toxicity can lower the seizure threshold, uncontrolled epilepsy is a concern.
- Certain chemotherapy agents. Some drugs, including bleomycin and doxorubicin, can interact dangerously with hyperbaric oxygen. A complete medication review is essential.
- Severe claustrophobia. While not a medical contraindication, significant claustrophobia can make chamber sessions intolerable. Discuss this with the clinic, as clear chambers and preparation often help.
- Untreated high fever or significant respiratory infection. These are generally reasons to postpone, not absolute contraindications.
Pregnancy deserves special mention. HBOT is generally avoided during pregnancy unless the benefit clearly outweighs the risk, as in carbon monoxide poisoning where both mother and fetus are in danger. Elective HBOT during pregnancy is not recommended.
Fire safety
One of the most serious risks in hyperbaric medicine is fire. In an oxygen-enriched environment, materials burn faster and hotter than in normal air, and even a small ignition source can cause a catastrophic fire. This is why chambers have strict rules about what can go inside.
Reputable clinics enforce these rules rigorously: no electronics, no petroleum-based products, no synthetic clothing that generates static, no lighters or matches. Patients change into approved cotton clothing. The chamber itself is designed with fire safety in mind, and staff are trained in emergency procedures.
As a patient, your role is simple: follow the rules exactly, even if they seem inconvenient. They exist because the physics of oxygen-enriched fire is unforgiving.
What responsible screening looks like
Before your first session at a trustworthy clinic, you should encounter a real medical screening process. This typically includes a health history questionnaire, a review of your medications, questions about lung conditions, ear history, seizure history, and current symptoms like congestion or infection.
For post-surgical patients, screening should also cover the procedure, the date, the current state of healing, and whether your surgeon is aware of your HBOT plan. The clinic should be willing to coordinate with your surgeon or request clearance.
If a clinic skips screening, rushes through it, or treats it as a formality, consider that a serious warning sign. Proper screening is how responsible providers keep a safe therapy safe.