Swimmer’s ear is caused by water getting trapped in the ear canal, which breaks down the skin’s natural defenses and allows bacteria to multiply. The two bacteria most often responsible are Pseudomonas aeruginosa and Staphylococcus aureus, though fungal organisms can occasionally be involved. With an estimated 4.67 million cases per year in the United States alone, it’s one of the most common waterborne conditions.
How Water Leads to Infection
Your ear canal has a surprisingly effective self-defense system. It’s lined with tiny hairs, coated in earwax, and maintained at a slightly acidic pH (between 5.2 and 7.0) that discourages bacterial and fungal growth. Earwax itself contains immune proteins, enzymes, and lipids that actively fight off microorganisms. Under normal conditions, bacteria live on the surface of the ear canal without causing problems.
When water sits in the canal for a prolonged period, it softens and breaks down this protective skin lining, a process called maceration. The moisture also dilutes earwax and shifts the canal’s pH toward a more neutral, bacteria-friendly range. Once the skin barrier is compromised, bacteria that were previously kept in check begin to multiply rapidly. The result is swelling, redness, and pain that typically develops within 48 hours of the initial exposure.
Swimming is the most obvious source of trapped water, but it’s not the only one. Heavy perspiration, high humidity, and even long, hot showers can create the same moist environment inside the ear canal.
Cotton Swabs and Other Physical Causes
Water isn’t always the starting point. Anything that scratches or irritates the delicate skin lining the ear canal can open the door to infection. Cotton swabs are one of the most common culprits. Using them to clean inside your ears can create tiny cuts in the canal lining, push wax deeper (forming a plug that traps moisture behind it), and strip away the protective earwax layer that keeps bacteria in check. Otolaryngologists have long warned against the practice for exactly these reasons.
Earbuds, hearing aids, and earplugs pose a similar risk. They can cause small areas of friction or pressure against the canal wall, and they also block airflow, trapping humidity inside. If you wear hearing aids daily or use earbuds for hours at a time, you’re creating conditions where moisture accumulates and the skin stays slightly irritated, both of which favor bacterial overgrowth.
Fingernails, bobby pins, and other objects people use to scratch an itchy ear can do the same kind of damage. Even a single small abrasion is enough to let bacteria past the skin barrier.
Anatomy That Increases Risk
Some people are simply more prone to swimmer’s ear because of the shape of their ear canals. Narrow or unusually curved canals don’t drain water as easily and trap moisture longer. People who swim regularly in cold water face an additional risk: the repeated cold exposure can stimulate bony growths called exostoses inside the ear canal. These small, benign bumps narrow the canal over time, leading to chronic problems with wax buildup, poor drainage, and recurrent infections. Surfers and open-water swimmers are especially affected.
As exostoses grow, they create pockets where water and debris collect. Patients with significant narrowing often deal with repeated episodes of swimmer’s ear, ear fullness, and gradual hearing loss on the affected side.
Earwax Removal and Disrupted Defenses
Earwax gets a bad reputation, but removing it too aggressively is one of the more overlooked causes of swimmer’s ear. The wax forms a water-repellent, acidic coating that lines the outer third of the ear canal. It contains antibacterial and antifungal compounds, including immune proteins called immunoglobulins. When you strip this layer away through frequent cleaning, the canal loses its chemical shield.
People who clean their ears daily, whether with swabs, ear picks, or irrigation kits, often find they produce more wax in response, creating a cycle of cleaning and overproduction that leaves the canal chronically irritated. That irritated, wax-depleted canal is far more vulnerable to infection the next time water gets in.
What Swimmer’s Ear Feels Like
The infection typically announces itself with itching inside the ear, followed by increasing pain that worsens over a day or two. A hallmark sign is pain when you press on the small flap of cartilage in front of the ear canal (the tragus) or when you pull on the outer ear. This distinguishes swimmer’s ear from a middle ear infection, which doesn’t usually hurt with external touch.
As the infection progresses, you may notice:
- Swelling that partially closes off the ear canal
- Discharge that can be clear, white, or yellowish
- Muffled hearing on the affected side
- Pain that worsens with chewing or jaw movement
- A feeling of fullness or pressure in the ear
In more severe cases, redness and swelling can spread beyond the ear canal to the outer ear and surrounding skin. Roughly 567,000 emergency department visits per year in the U.S. are attributed to acute swimmer’s ear, and about 23,200 cases are serious enough to require hospitalization.
Preventing Trapped Moisture
Since trapped water is the primary trigger, the most effective prevention strategy is keeping the ear canal dry. After swimming or showering, tilt your head to each side and let gravity pull water out. A hair dryer on its lowest heat setting, held at arm’s length, can help evaporate residual moisture.
A simple homemade preventive drop can be made by mixing equal parts rubbing alcohol and white vinegar. A couple of drops in each ear after water exposure serves two purposes: the alcohol binds with trapped water and helps it evaporate faster, while the vinegar restores the canal’s acidic pH to discourage bacterial growth. People who get repeated infections may benefit from using these drops after every shower, not just after swimming.
Equally important is leaving earwax alone. Avoiding cotton swabs and other objects inside the ear canal preserves the natural wax barrier and prevents the micro-injuries that invite infection. If you wear hearing aids or use earbuds frequently, removing them periodically to let air circulate through the canal can help reduce moisture buildup.