Can You Scuba Dive With Asthma? What Doctors Check

A reliever inhaler used on Saturday afternoon rules out a Sunday morning dive under British Thoracic Society guidance, because it shows asthma was active in the 48 hours before. Many people with asthma can scuba dive, provided the condition is well controlled and their lung function tests normal. Wheeze set off by exercise, cold or emotion is where the guidance says no, and so is a history of severe or unpredictable attacks.

The decision starts with a paper form and usually ends in a doctor's rooms, with spirometry and an exercise test. The diagnosis alone settles surprisingly little. Airway behaviour under load settles most of it.

Why is asthma a concern underwater?

The core risk is trapped gas on the way up. Air in the lungs expands as water pressure falls during ascent, and a diver normally vents it by breathing out. Narrowed or mucus-plugged airways can stop part of the lung emptying fast enough, so that section overinflates and can tear. DAN lists the possible results as pneumothorax or arterial gas embolism, where gas escapes into the bloodstream. Holding your breath on ascent causes the same injury through the same physics. The difference is that asthma can close the airway without the diver choosing it.

Breathing also gets harder with depth. Denser gas raises the work of breathing. DAN Southern Africa puts maximum breathing capacity at about 70% of its surface value at 10 metres, and about half at 30 metres. The BTS guideline cites chamber work showing maximum voluntary ventilation cut by more than 50% at a simulated 30 metres. Healthy airways rarely notice, since recreational diving tends to run at a modest workload. Airways that narrow mid-dive leave far less in reserve when a current picks up.

The dive itself supplies the classic triggers. Cylinder air arrives cold and dry, a hard swim raises the breathing rate, and seawater breathed in through a leaking regulator can provoke bronchospasm. Anxiety, too. In 1995 the journal Chest described two cases of cerebral air embolism in people with asthma during scuba training in a swimming pool. Shallow water, in other words, isn't automatically safe water.

What does "well controlled" mean to a dive doctor?

The UHMS physician guidance cites one benchmark: the British Thoracic Society's 2003 guideline, written for physicians assessing divers. It permits diving for people with asthma who pass three tests, whether or not they use a regular preventer inhaler. It then adds rules for the diving season, because a good clinic result doesn't prevent a later flare.

No current symptoms. The person is free of asthma symptoms.
Normal spirometry. FEV1 above 80% of predicted, and an FEV1/VC ratio above 70% of predicted.
A negative exercise test. FEV1 falls by less than 15% after exercise, which is the nearest a clinic gets to a hard fin kick into current.
Twice-daily peak flow in the diving season. No diving after needing relief medication in the previous 48 hours, with peak flow more than 10% below personal best, or with more than 20% variation across the day.

The physician guidance published with the diver medical form lands in the same place. It names the exercise test as the best way to assess fitness and rates inhalation challenge tests as too poorly standardised for diving decisions. Anyone cleared on that basis keeps taking their regular inhalers and sits out any dive while symptoms suggest a flare. A clearance works like a C-card: it proves a good day in the clinic. The peak flow reading on the morning of the dive is the logbook entry that counts.

Which kinds of asthma rule diving out?

Wheeze triggered by exercise, cold or emotion is the clearest line. The BTS guideline and the physician guidance both advise against diving with those triggers, because a dive can deliver all three at once. That guidance also classes people with a history of severe or unpredictable attacks as unfit to dive. On the other side, DAN summarises the Undersea and Hyperbaric Medical Society view that mild intermittent, mild persistent and moderate persistent asthma may be compatible with diving when well controlled.

Asthma triggered only by allergy sits in a narrower middle ground. The BTS allows diving where allergy is the sole trigger and lung function is normal. It also records an odd case from 1999: a diver allergic to Parietaria pollen had an attack at depth. His cylinder had been filled with unfiltered air carrying that same pollen. One bad fill turned a manageable allergy into an emergency.

Are divers with asthma more likely to be injured?

Nobody knows precisely, and the numbers point in different directions. A 1991 Australian review found nine asthmatics among 100 diving deaths in Australia and New Zealand, when fewer than 1% of divers there reported asthma. A US survey by Neuman and colleagues found that 5.3% of 696 divers had been diagnosed with asthma, close to the general population rate. A case-control study of 196 arterial gas embolism cases produced odds ratios of 1.58 for any asthma and 1.98 for current asthma. Neither figure reached statistical significance.

A 2016 review in the European Respiratory Review found no epidemiological evidence of higher injury or death rates among divers with asthma. The authors flag the catch themselves. Most of the data describe people with mild asthma who chose to dive under existing guidelines, so the true risk for poorly controlled asthma may be higher. Screening shapes the evidence, which means the evidence can't be used to argue screening away.

How does the diver medical form handle asthma?

PADI courses and programmes start with the Diver Medical Participant Questionnaire, created by the Diver Medical Screen Committee in association with UHMS, DAN and DAN Europe. Box A asks about "asthma, wheezing, severe allergies, hay fever or congested airways within the last 12 months" that limit exercise. A yes sends the form to a doctor. So does a yes to question 10 on current prescription medication, which means a prescribed preventer inhaler leads to a medical evaluation even in a symptom-free year.

The screening system's FAQ, published by UHMS, explains the design. Doctors focus on control and triggers rather than the label, and inhaler use alone isn't meant to disqualify anyone. The physician then marks the form Approved or Not Approved. Nothing in between. PADI's forms page states that a doctor can't add limits or conditions, and dive professionals must treat a conditional approval as Not Approved. A note reading "fine for shallow dives" is, on paper, a no.

What's the sensible next step?

Answer the form honestly, then take it to a doctor trained in dive medicine. DAN Southern Africa keeps a dive doctor listing for the region and offers medical information and referrals. Assessment typically includes spirometry, often with a reversibility test, and an exercise test. The 2016 review describes exercise to about 75% of predicted maximum capacity. The same questionnaire comes first for a Discover Scuba Diving session and for the Open Water Diver course. Sorting the medical before choosing a course date saves a wasted booking.

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Frequently Asked Questions

Can you use a reliever inhaler before a dive to prevent symptoms?
The guidance is built around not needing one. BTS advice is to skip diving if symptoms needed relief medication in the 48 hours before, so a reliever can't cover for active asthma. Cleared divers keep taking their regular preventer medication, and DAN suggests keeping inhalers on the boat.

Does childhood asthma mean you need a dive medical?
The questionnaire asks about symptoms in the last 12 months that limit exercise, and about current prescription medication. Someone with no symptoms and no medication for years may answer no to both. The BTS guideline still asks doctors to record childhood history, so a dive doctor is the right person to settle any doubt.

Why is scuba air a problem for asthma?
Scuba air is dry, and it cools as it expands from cylinder pressure through the regulator. The physician guidance describes cold air breathing as the normal case in scuba, which is why cold-induced wheeze is a firm exclusion. Heavy breathing during a hard swim pushes more of that cold, dry gas through the airways.

Can hay fever stop you from diving?
Hay fever or congested airways that limited exercise in the last 12 months is a yes in Box A, so a doctor sees the form. Wheeze triggered only by allergy, with normal lung function, is compatible with diving under BTS guidance. Congestion also makes ears harder to clear, as covered in equalising your ears when scuba diving.

Do divers with asthma get decompression sickness more often?
One DAN survey of 279 divers with asthma, covering 56,334 dives, recorded 11 cases of decompression sickness in eight divers, a rate above the estimate for unselected divers. The 2016 review notes that no physiological link between decompression sickness and lung overexpansion injury has been established, so the finding is hard to read. The mechanics of decompression sickness and decompression illness are a separate problem from trapped gas.

Can children with asthma learn to dive?
Junior divers on PADI courses complete the same Diver Medical form, signed by a parent or guardian. Youth programmes such as Bubblemaker and Seal Team use their own statement and medical questionnaire. The trapped-gas physics are the same at any age, so control and triggers stay the deciding questions.

This is general information, not a substitute for a dive medical or advice from a doctor trained in dive medicine. In an emergency, contact DAN Southern Africa on its 24-hour hotline, +27 82 810 6010.

Reviewed September 2026. Devon Ford runs Scuba Evolution, a PADI 5 Star Dive Centre in Glenvista, Johannesburg.