Swimmer's ear is an infection of the outer ear canal, and the NHS names water in the ear as one of its causes, which is why it often follows days of pools, sea swims and diving. Keep your ears dry, never clean them with cotton buds, and stay out of the water until it has cleared; most cases settle within three days to a week, but some signs mean a doctor the same day.
The medical name is otitis externa. It affects the ear canal, the passage between the outer ear and the eardrum, and it is a different problem from the pressure injury divers call ear squeeze. On a Thai island holiday, with several swims a day, the ear canal can stay wet for much of the trip. This page explains what causes the infection according to the NHS, how to prevent it, what a pharmacy or doctor can do, and how to handle diving and flying with sore ears.
What causes swimmer's ear
The NHS says an outer ear infection is caused by something irritating the ear canal, and lists four causes: eczema, water, wearing earplugs, and a fungal or bacterial infection. It affects children and adults. Note what is not on that list: the NHS does not name hot weather or humidity as causes, so the risk on a beach holiday comes from the swimming itself, and from anything that scratches or irritates the canal.
The symptoms usually start quickly. The NHS lists earache, discharge from the ear, a feeling of pressure or fullness, itching and irritation in and around the ear, and scaly skin. Earache has other causes too, from earwax to a perforated eardrum, and the NHS warns against trying to diagnose the cause yourself.
Prevention: keep the canal dry and leave it alone
The NHS advice for preventing ear infections is short and practical:
- Do not put cotton buds or fingers in your ears, even to dry them after a swim.
- Use earplugs or a swimming hat over your ears when you swim.
- Keep water and shampoo out of your ears in the shower; the NHS suggests cotton wool smeared with petroleum jelly.
- Get eczema or allergies that affect your ears treated; our page on skin rashes and infections covers skin problems on a hot-weather trip.
Earplugs appear on both NHS lists, as a way to keep water out and as a possible irritant. If you use them, keep them clean and stop if your ears itch or hurt. A pair belongs in a travel first-aid kit for Thailand anyway. Divers should read the next section first, because solid earplugs and diving do not mix.
Tilt and let it drain, do not dig. Water trapped after snorkeling or a pool session is tempting to chase out with a cotton bud or a corner of a towel. The NHS says not to put anything inside your ear, and irritation of the canal is what it links to infection. Tilt your head and let the water run out, and dry only the outer ear.
Diving and snorkeling: ear squeeze is a different problem
The CDC says the most common injury in divers is middle ear barotrauma, or "ear squeeze": on the way down, the pressure in the middle ear fails to equalize with the water pressure, which strains the eardrum. Forcing equalization too hard can damage the inner ear, and the CDC names solid earplugs and overuse of decongestant sprays among the risk factors. That is a pressure injury behind the eardrum, not an infection of the canal, though both can make your ear hurt after a day on the boat.
The practical rule is the same for both: if an ear hurts, has fluid coming from it, or your hearing has changed, stop diving and get it checked. Our guide to dive safety and recompression chambers covers diving emergencies, and the page on snorkeling safely covers the day-trip boats. If you are doing a course, such as learning to dive on Koh Tao, tell the instructor about any ear problem before the next dive.
Pharmacy drops and self-care
The NHS says a pharmacist or doctor may give antibiotic tablets, or antibiotic, antifungal or steroid ear drops, depending on the cause. Thai pharmacies are a sensible first stop for a mild, itchy ear without fever; our article on what Thai pharmacies sell over the counter explains how they work. Show the pharmacist which ear hurts and how long it has done so, and ask how to use the drops: the NHS warns that ear drops may not work if they are not used correctly.
While it heals, the NHS advises:
- painkillers such as paracetamol or ibuprofen, following the pack or the pharmacist (children under 16 should not take aspirin)
- wiping away any discharge with cotton wool, outside the ear only
- not putting anything inside the ear, and keeping water and shampoo out
- no swimming until the infection has gone
Decongestants and antihistamines do not help ear infections, the NHS says. If you want to buy a decongestant for a blocked nose, note that pseudoephedrine is a controlled medicine in Thailand, which matters if you plan to bring some from home; our guide to bringing medicine into Thailand explains the rules.
Red flags: when to see a doctor the same day
An ear infection with fever or swelling needs a doctor, not drops. The NHS says to get urgent help if you have ear infection symptoms and a very high temperature or feel hot and shivery, swelling around the ear, fluid coming out of the ear, a change in hearing or new hearing loss, or vomiting, dizziness or a severe sore throat. The same applies to a baby under 12 months with pain in both ears, and to anyone with diabetes, a heart, lung, kidney or neurological condition, or a weakened immune system.
In Thailand, "urgent help" means a hospital emergency department or a clinic that day; our guide to hospitals in Thailand explains the choice between private and public care. If the earache is milder but has not improved after three days, or keeps coming back, see a doctor at your next convenient chance. On a small island with no hospital, take the next boat rather than waiting it out; our page on late-night pharmacies covers what is open after dark.
Flying with ear pain
The CDC says air travel can cause barotrauma, most often in the middle ear, when a blocked eustachian tube stops pressure equalizing during climb and descent. It is usually not severe or dangerous, but rarely leads to dizziness, hearing loss, a perforated eardrum or lasting ringing in the ears. The CDC says travelers with ear, nose or sinus infections or severe congestion might choose to postpone flying, or use decongestants to ease the symptoms.
If you have an ear infection and a flight coming up, ask a pharmacist or doctor before you fly; they can tell you whether to travel and what is safe to take. A domestic hop between islands is easy to move by a day or two, so it is worth asking early rather than at the gate.
Frequently asked questions
Can I swim with swimmer's ear?
No. The NHS advises against swimming while you have an ear infection, and says to keep water out of the ear until it has cleared. Most outer ear infections clear within three days, though symptoms sometimes last up to a week.
Does the heat in Thailand cause ear infections?
The NHS does not list heat or humidity as causes. It names water, earplugs, eczema and fungal or bacterial infection. On a beach holiday, the main risk is frequent swimming and anything that irritates the ear canal, such as cotton buds.
Can I buy ear drops at a Thai pharmacy?
Thai pharmacies sell medicines over the counter, and the pharmacist can advise on drops for a mild outer ear infection. See a doctor instead if you have a fever, swelling, discharge or hearing changes, or if it has not improved after three days.
Is swimmer's ear the same as ear squeeze from diving?
No. Swimmer's ear is an infection of the outer ear canal. Ear squeeze, or middle ear barotrauma, is a pressure injury that the CDC calls the most common injury in divers. Both can hurt, and both are reasons to stop diving and get checked.
Sources
- NHS – Ear infections (last reviewed 16 January 2025) (checked October 2026)
- NHS – Earache (checked October 2026)
- CDC Yellow Book – Scuba diving: decompression illness and other dive-related injuries (checked October 2026)
- CDC Yellow Book – Air travel (checked October 2026)