Decongestants Before Diving: Trouble on the Way Up

It tends to come up over coffee before the first dive: a sinus tablet at breakfast, to help the ears. The first descent goes fine. On the second ascent, one ear stops venting, and the pressure builds with every metre.

Taking a decongestant to get your ears through a dive is a bet on timing. It shrinks swollen lining for a few hours. If it wears off before you surface, the passages can close and trap expanding air on the ascent, which is a reverse block. DAN's advice starts with not diving congested, and a doctor's view before any medication.

Can you take Sudafed or a decongestant before diving?

Not as a way to push congested ears through a dive. DAN's medication guidance says divers who need decongestants to equalise face "an increased risk of serious injury from barotrauma", and its sinus guidance sends them to a doctor. The habit is common anyway: research cited in a 2014 Hawaiian study puts routine use at 6% to 25% of divers.

Dive medicine doesn't issue a blanket ban. The UK Diving Medical Committee says a pseudoephedrine tablet may help some divers. It considers one safe shallower than about 30 metres, after a trial on land a day or two before. The case this article is about is narrower: a tablet or spray on dive morning, to open passages that are blocked that morning. DAN's checklist for doctors flags the medication wearing off at depth.

At Scuba Evolution we don't recommend taking medication to get through a dive. The reverse blocks we see tend to follow one pattern. A diver feeling a little under the weather takes a decongestant and dives while it keeps them clear, then the passages close again on the way up. Any medicine is your doctor's call, not ours.

Why can a decongestant cause a reverse block?

Because it works on a timer, and the ascent is the half of the dive you can't skip. Pseudoephedrine tablets and oxymetazoline or xylometazoline sprays constrict blood vessels in the lining of the nose, sinuses and Eustachian tubes, so the lining shrinks and the passages open. When the drug wears off, DAN Southern Africa explains, the vessels can swell with more blood than before.

Coming up, the air in your middle ears and sinuses expands and has to vent through those openings. DAN's ear reference lists decongestants that wear off at depth among the usual causes of a reverse squeeze, with poor equalising and diving congested. A descent can be stopped. An ascent can only be slowed.

Nobody can time it. SAHPRA-approved information for a Sinutab tablet gives pseudoephedrine a half-life of 5.5 to 7 hours in adults. Urine acidity shifts that, and one study measured anything from 1.9 to 21 hours. DAN puts most sprays at eight to 12 hours, which a two-dive morning can outrun.

What's in Sinutab, Sudafed, Sinumax and Sinuclear?

Pseudoephedrine, in every tablet and syrup we checked, usually with a painkiller and sometimes a sedating antihistamine. One brand covers several formulas, so read the ingredients. The table shows what South African package inserts and a pharmacy listing state, as information, not a recommendation.

Each extra ingredient adds a diving problem. The Sudafed Sinus Pain leaflet lists nervousness, restlessness, poor sleep, anxiety and palpitations, and DAN adds a rapid heartbeat. Chlorphenamine and codeine bring drowsiness, and DAN warns that drugs like these can interact with nitrogen narcosis unpredictably. Paracetamol dulls pain without fixing its cause. The inserts also rule out MAOI antidepressants, most heart conditions, raised blood pressure and a second cold remedy. The tablets are Schedule 2 medicines here, so the pharmacist can check them against anything else you take.

For nitrox divers, a DAN study found that high doses of pseudoephedrine brought on oxygen seizures sooner in male rats breathing pure oxygen; lower doses didn't. It's rat data, not proof of a human risk.

Can you use a nasal spray before diving?

A decongestant spray carries the same wear-off risk, plus a rebound that can outlast the cold, and DAN warns that repeated use can set up a reverse block. In April 2026 the UK regulator, the MHRA, limited oxymetazoline and xylometazoline sprays to five consecutive days, down from seven. People can mistake the rebound for the original cold and keep spraying, it warned, which can lead to rhinitis medicamentosa, a lasting congestion. The pharmacy listing for the Sinutab spray says three days at most.

Steroid sprays don't rebound but take about a week to work, says DAN Southern Africa, and whether one suits you is a doctor's call. Our guide to diving with a cold or blocked sinuses covers them.

What does a reverse block feel like, and what should you do?

Pressure, fullness or pain in an ear as you rise, sometimes with vertigo. In a sinus, DAN describes sharp facial pain on the ascent, then a nosebleed or blood in the mask. Vertigo is the dangerous part. DAN says up to 25% of divers experience alternobaric vertigo, and losing track of up and down makes a controlled ascent harder. What DAN advises:

• Stop rising. Signal "something is wrong" and point at the ear, so your buddy stays close.
• Go down a little. Descend until the pain eases, then try to open the tube.
• Try a gentle technique. Pinch your nose and swallow, the Toynbee, which DAN rates for ascent. Turning the blocked ear towards the bottom may help.
• Come up in small steps. Ascend as slowly as your air allows. In a DAN case report, an assistant instructor took about 10 minutes to work the air out.
• Keep going if it won't clear. DAN notes that in rare cases the block lasts all the way up.

DAN's comment on that case: good buoyancy control can make the difference between an ear injury and none. Afterwards, don't dive while an ear feels full. See a doctor for vertigo or lasting pain and fullness, and an ENT specialist if reverse blocks recur, says DAN. Severe vertigo that persists after a dive is an emergency. Our guide to blocked ears after a dive covers the warning signs.

How do you clear your sinuses and prepare your ears before diving?

Start days early, with technique rather than chemistry. None of it treats a cold. The UK Diving Medical Committee suggests inflating your ears several times a day for three to four days before diving, though not with a cold. On the day, DAN's tips are to listen for a pop in both ears when you swallow, then equalise gently on the surface and often on the way down. Our guide to equalising your ears has the full routine.

A 2018 Cochrane review of 14 trials found saline rinses may ease allergic rhinitis, with no adverse effects reported, though on weak evidence. A Cochrane review couldn't show that steam relieves colds. DAN's tips add that smoke and alcohol irritate the lining. No study we found shows drinking water opens a Eustachian tube, but dehydration carried 2.7 times the odds of decompression sickness in the Hawaii study.

At Scuba Evolution we also suggest a menthol or eucalyptus nasal inhaler for a few days before a trip, alongside saline, as a comfort and a prompt to start early. In laboratory studies, menthol, camphor and eucalyptus vapour made nasal breathing feel clearer without changing measured nasal resistance, and a menthol lozenge did the same for 62 people with colds. The cool feeling is real; the wider airway isn't. An inhaler doesn't replace being clear on the day. Read the label too: some US inhaler sticks list levmetamfetamine, a decongestant, as the active ingredient.

What to do before your next dive

Congested on the morning of a dive means another day. If you regularly need something to clear your ears, see a doctor trained in dive medicine before the trip; SAUHMA lists dive medical examiners in South Africa. Holding a depth with your breath and rising in small steps is the control Peak Performance Buoyancy (R3,800) trains. The Nitrox course (R3,200) covers planning a nitrox dive. Ears that keep causing trouble are covered in bad ears and scuba.

Sources

• DAN, Sinus Barotrauma. Prevention, the reverse block, medication and spray rebound. Also DAN's Over-the-Counter Medications and the Alert Diver article on diving with medication.
• DAN, The Ears & Diving: Injuries. Reverse squeeze and alternobaric vertigo. Also Equalization, the reverse block case summary and DAN's 10 tips for equalizing on the PADI blog.
• DAN Southern Africa, Nasal Decongestants FAQ. Rebound and steroid sprays.
• DAN, Decongestants and Diving, summarising Pilla et al., Neuroscience 2013, on pseudoephedrine and oxygen seizures in rats.
• SAHPRA repository, Sudafed Sinus Pain leaflet (2024) and Sinutab Sinus Pain Non-Drowsy professional information (2022). Ingredients, side effects and the half-life.
• MHRA Drug Safety Update, April 2026. Rebound congestion and rhinitis medicamentosa.
• UK Diving Medical Committee, Diver Ear Clearing.
• Burrow A, Eccles R, Jones AS. Acta Otolaryngol 1983 and Eccles R et al. J Pharm Pharmacol 1990 on menthol. Also Head K et al., Cochrane 2018, on saline irrigation and Smerz RW, Hawaii J Med Public Health 2014, on decongestant use in divers.

Frequently Asked Questions

Is it OK to take Sudafed before scuba diving?
Not to push congested ears through a dive. DAN sends that decision to your doctor and warns the drug can wear off at depth, causing a reverse block. The UK Diving Medical Committee is more permissive but says to try it on land first.

Can you use a nasal spray before diving?
Decongestant sprays can wear off at depth too, and overuse causes rebound congestion; the UK regulator limits them to five consecutive days. Steroid sprays don't rebound but take about a week to reach full effect. Ask your doctor.

What is a reverse block in diving?
Barotrauma on the way up. Air in the middle ear or a sinus expands as you rise and can't vent, often because congestion or a worn-off decongestant has closed the passage. It brings pressure, pain and sometimes vertigo.

How do you fix a reverse block underwater?
Stop rising, signal your buddy and descend a little to ease the pressure. Pinch your nose and swallow, then ascend in small steps as slowly as your air allows. See a doctor afterwards for vertigo or pain that lasts.

How do you clear your sinuses before diving?
You don't dive while they're blocked. For slow ears, practise equalising several times a day for three to four days beforehand. Saline rinses may ease allergies. A menthol inhaler feels clearing, but in studies it didn't change measured nasal resistance.

Can you take pseudoephedrine before a nitrox dive?
Ask your doctor. In a DAN research study, high doses brought on oxygen seizures sooner in male rats breathing pure oxygen; lower doses didn't. The researchers advised against exceeding the recommended dose before nitrox or oxygen diving.

General information only, not medical advice. Ask your doctor or pharmacist, and a doctor trained in dive medicine, before diving on any medicine. In an emergency, call the DAN Southern Africa 24-hour hotline on +27 82 810 6010.

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