Can You Scuba Dive With Asthma? What Medical Guidelines Say

Can you scuba dive with asthma?

Many people with asthma do. Divers with asthma used to be excluded as a rule, but a 2016 review in the European Respiratory Review says field experience and published data do not support that dogmatic approach. It puts asthma at about 7% of the general population, with probably a similar share among divers.

The UK Diving Medical Committee (UKDMC) says carefully selected asthmatics can probably dive safely, and that the aim of its assessment is to exclude people with unstable airways.

The medical form decides if you need a doctor at all, and our diver medical questionnaire guide explains how it works. This page covers what comes next: the guidelines, the tests and the rules for dive days.

This is general information, not medical advice. A physician decides fitness to dive, ideally one trained in diving medicine. DAN's Medical Information Line (+1 919 684 2948, option 4, weekdays 8:30 a.m. to 5 p.m. US Eastern time) answers fitness-to-dive questions. More health topics are in our safety guides.

Why is asthma a concern underwater?

There are two main risks: lung rupture on the way up and running out of breath at depth. DAN explains that narrowed airways can trap gas during ascent. If it expands faster than it can be breathed out, the lung may rupture and cause arterial gas embolism or a collapsed lung (pneumothorax). UKDMC adds that mucus plus bronchospasm can block airways this way, with potentially fatal results.

Breathing also gets harder with depth because the gas gets denser. The BTS guideline cites chamber work in which maximum voluntary ventilation at a simulated 30 m (100 ft) fell by more than 50%, and UKDMC says that at 30 m a diver uses about half the available exercise capacity just to breathe. DAN notes that underwater you cannot always stop and catch your breath, and warns of panic and drowning, including at the surface.

Diving also supplies the triggers. SPUMS lists exercise, inhaled seawater and cold, dry air, plus the fine seawater mist a regulator can produce, a salty (hypertonic) aerosol that may narrow the airways. In a small study summarised by Adir and Bove, a single 5 m (16 ft) pool dive lowered lung function in divers with asthma compared with healthy divers.

What the guidelines say: UK, US, Australia and Europe compared

They agree on the core idea. Stable asthma with normal lung function and a clean exercise or challenge test may be acceptable, and symptoms on the day are not. They differ on thresholds, on which tests to use and on how far back your history counts.

The British Thoracic Society (BTS) guideline dates from 2003 but is still the reference others quote: the 2023 US physician guidance repeats its main asthma recommendation almost word for word. All of the BTS asthma recommendations carry grade C, the guideline's label for advice that rests on expert opinion because directly applicable studies of good quality are absent.

In Europe, the European Diving Technology Committee (EDTC) standard is written for working divers, including recreational dive professionals. For recreational screening it points to the Diver Medical Screen Committee (DMSC) questionnaire, which it lists as approved by WRSTC, CMAS, UHMS and DAN.

What tests will a diving doctor use?

Spirometry is the starting point everywhere. Challenge testing is where guidelines split. SPUMS recommends it after any asthma in the last ten years when spirometry is normal. The US guidance says inhalation challenges with histamine, hypertonic saline or methacholine are not standardised enough to interpret for scuba diving, and calls an exercise test the best way to assess fitness. The BTS does not support routine challenge testing, and Adir and Bove say it has been abandoned in most countries because of a high false-positive rate.

• Spirometry: you breathe out hard into a meter that records FEV1 (the volume blown out in the first second), FVC (the total) and peak flow. Pass marks sit at about 80% of predicted, with an FEV1/FVC ratio above 70% (BTS, UKDMC) or 75% (SPUMS).
• Exercise test: the BTS withholds bronchodilators for 24 hours, then measures FEV1 at 1, 3, 5, 10, 15, 20 and 30 minutes after exercise. A fall of 10% or more is abnormal; 15% or more is diagnostic of exercise-induced bronchoconstriction and would contraindicate diving. UKDMC uses a Chester step test (level 4, then level 5 for 5 minutes) at 80-90% of maximum heart rate, ideally breathing dry air from a scuba tank, with spirometry at 5, 10, 15 and 30 minutes.
• Bronchial provocation (challenge) test: you inhale something that irritates sensitive airways and the fall in FEV1 is measured. SPUMS describes indirect challenges (exercise, dry-air breathing, mannitol or 4.5% saline) as more specific. A fall above 15% means advice against diving, with re-testing allowed once the asthma is controlled.
• Peak flow diary: UKDMC asks for two weeks of readings before the exercise test. SPUMS calls peak flow meters of limited use for judging fitness to dive but useful for day-to-day monitoring.

Can you dive with exercise-induced asthma?

The guidelines disagree here. The BTS guideline and the US physician guidance both say people whose wheeze is brought on by exercise, cold or emotion should be advised not to dive. The US guidance lists respiratory impairment from cold gas breathing as a severe risk, while asthma and exercise-induced bronchospasm sit under relative risk.

UKDMC takes a treatment-first route. Its 2024 algorithm sends a diver whose asthma is caused by cold air, emotion or exercise to optimise treatment, keep a two-week peak flow diary and then take an exercise test. If variation stays under 15%, the outcome is fit to dive, with the risks explained. SPUMS reaches a similar place another way: a positive challenge test means advice against diving for now, but re-testing after treatment is allowed, and SPUMS says current data suggest the response can normalise with treatment.

Exercise and cold matter because scuba air is cold and dry. The US guidance says the candidate must not be impaired after exercise or cold air breathing, 'which is the normal case of gas expanding from within a scuba cylinder'. The UKDMC test protocol treats dry air like cold air as a trigger.

Inhalers, relievers and peak flow on dive days

If you are cleared, keep taking your regular inhalers. The US guidance says cleared divers need to take them and should not dive with symptoms that suggest a flare-up. UKDMC accepts inhaled steroids, long-acting beta-2 agonists and leukotriene antagonists.

A reliever puff before the dive is contested, so ask your diving doctor. UKDMC says taking a reliever half an hour before diving may be a good idea to lower the risk of bronchospasm. SPUMS lists the possibility that bronchodilators help bubbles pass the lung's filter and so predispose a diver with asthma to decompression illness. In a 1990 survey of 104 divers with asthma who answered a diving magazine questionnaire, quoted by the BTS, 96 took a beta-2 agonist before diving. That shows what divers did, not whether it was safe.

The day-to-day rules, with the guidelines' own numbers:

• Measure peak flow twice a day, for at least three days before diving and throughout the diving period (UKDMC).
• Skip the dive if peak flow is more than 10% below your best (BTS, SPUMS). UKDMC uses 15% below your normal best, then waits until it has been normal for 48 hours.
• No diving within 48 hours of needing a reliever. The BTS calls symptoms that needed relief medication in the 48 hours before a dive active asthma. UKDMC waits until peak flow has been normal for 48 hours, and the EDTC standard also sets 48 hours.
• Abandon the dive if you become short of breath or wheezy, at the surface or underwater (UKDMC).
• Ascend slowly, within your computer's ascent rate, and make the last 5 m (16 ft) very slow (UKDMC).
• Keep your inhaler on the boat, ready to use, and tell the dive operator about it (DAN).
• After any change in asthma control, see your GP and then your diving physician before diving again (UKDMC).

What does the evidence on divers with asthma show?

Less than the detailed rules suggest. Adir and Bove describe most studies as retrospective, questionnaire based or reviews of accident registries, several key figures come from conference abstracts, and reviewers read the data differently.

A 2017 systematic review by Ustrup and Ulrik found seven studies with 560 subjects. Five reported a higher risk of diving injury in divers with asthma; two magazine surveys found none. The authors concluded that the evidence is limited but indicates increased risk. A 2023 update by Ledford repeated the search and reached the same conclusions, including that there are insufficient data to decide for an individual patient. Adir and Bove (2016) found no epidemiological evidence of a higher relative risk of lung barotrauma, decompression sickness or death, but warned that the data may be biased because they mostly describe people with mild asthma who chose to dive under the guidelines.

UKDMC's reading is that the asthmatics it allows to dive are probably no more at risk of decompression illness than the diving population as a whole. Overall diving fatality rates are in our article Is scuba diving dangerous?

Childhood asthma that has gone away

The form decides if you must mention it. The 2026 DMSC questionnaire asks, in box A, about asthma, wheezing, severe allergies, hay fever or congested airways within the last 12 months that limit your physical activity or exercise. The UKDMC declaration asks whether you have ever had asthma or ever used an inhaler, and any yes means seeking advice from a UKDMC Medical Referee.

Doctors look further back. The BTS asks for attention to childhood lung disease in the history. SPUMS asks for a challenge test after any asthma in the last ten years if spirometry is normal, and warns that a resolution of asthma during adolescence may be more apparent than real. Even with no wheeze or medication for ten years, it advises a low threshold for testing if exercise-induced symptoms are in doubt. UKDMC notes that asthma improves in many children during adolescence, so people with childhood asthma are less likely to meet the criteria before adulthood.

For children who still have asthma, the SPUMS paediatric position (for ages 10 up to 15, when adult guidelines take over) lists asthma, including well-controlled and exercise-induced asthma, among the conditions in its section on which young divers should not dive, noting that airway anatomy is not fully mature until 16. Age limits and readiness are covered in what age kids can start scuba diving.

Before you book a course: a checklist

Start a few weeks early. The UKDMC route alone includes a two-week peak flow diary before the exercise test.

• Get your asthma controlled with your own doctor first. SPUMS says any decision about diving should start from an established doctor-patient relationship for asthma care.
• Complete the medical form used where you will train. On the DMSC form, a prescribed inhaler also makes question 10 (current prescription medication) a yes, and that question sends you to a physician directly.
• See a physician trained in diving medicine. DAN's Medical Information Line gives referrals, and UKDMC lists its Medical Referees on its website.
• Start a twice-daily peak flow record and bring it, with your medication list and any past spirometry results.
• Ask which test is planned and stop bronchodilators only as the doctor tells you; the BTS exercise protocol withholds them for 24 hours.
• Declare asthma honestly. The UKDMC form warns that failing to declare a medical condition will invalidate your insurance; see what dive insurance covers.
• Choose easy conditions at first. Adir and Bove advise prudence in choosing where you dive, including temperature, currents and surface conditions.
• Book a yearly check. SPUMS advises annual review for divers with controlled asthma.