Swimmer’s ear happens when water, physical irritation, or loss of the ear canal’s natural defenses allows bacteria or fungi to infect the skin lining the outer ear. The condition accounts for roughly 2.4 million healthcare visits per year in the United States alone. While water exposure is the most well-known trigger, several other factors can set the stage for infection.
How the Ear Canal Normally Protects Itself
Understanding what causes swimmer’s ear starts with understanding what normally prevents it. Your outer ear canal is lined with hair follicles and small glands that produce cerumen, better known as earwax. Far from being just a nuisance, earwax is a sophisticated defense system. It contains antibacterial and antifungal compounds, including immune proteins and enzymes that actively kill microbes. It also maintains an acidic environment in the ear canal, with a pH between 5.2 and 7.0, which makes the canal inhospitable to most bacteria and fungi.
Earwax also forms a thin, water-repellent coating over the delicate skin of the canal, keeping moisture out and preventing the skin from softening and breaking down. When this protective layer is stripped away or overwhelmed, infection follows a predictable sequence: the skin barrier breaks down, the canal’s acidity drops, moisture accumulates, and bacteria begin to multiply.
Water Exposure Is the Primary Trigger
The reason this condition is called swimmer’s ear is straightforward. Prolonged or repeated water exposure is the single most common cause. When water sits in the ear canal, it softens and swells the skin in a process called maceration. This waterlogged skin develops tiny cracks and gaps that bacteria can penetrate. At the same time, the standing water dilutes and washes away the protective earwax, raising the canal’s pH and removing its chemical defenses.
Swimming in pools, lakes, or oceans creates the highest risk, but you don’t need to be a swimmer. Long showers, baths, or any activity that repeatedly gets water into your ears can have the same effect. Humid climates and heavy sweating also contribute by keeping the ear canal persistently damp. The combination of warmth and moisture creates an ideal breeding ground.
Cotton Swabs and Physical Damage
Inserting anything into the ear canal, whether it’s a cotton swab, a fingernail, a bobby pin, or a pen cap, can scratch or scrape the thin skin lining the canal. Even minor abrasions give bacteria a point of entry. Cotton swabs are a particularly common culprit because they also push earwax deeper into the canal, compacting it against the eardrum and stripping it from the walls where it does its protective work.
The irony is that aggressive ear cleaning actually increases your risk of infection by removing the very substance that prevents it. The ear canal is self-cleaning; earwax naturally migrates outward, carrying trapped debris with it. Disrupting this process does more harm than good.
Earbuds, Hearing Aids, and Earplugs
Any device that sits inside the ear canal for extended periods can raise your risk. Earbuds, hearing aids, and earplugs all block airflow and trap heat and moisture, creating a warm, humid microenvironment where bacteria and fungi thrive. These devices can also cause low-level friction against the canal skin, producing the same kind of micro-abrasions that cotton swabs cause.
If you wear hearing aids daily or use earbuds for hours at a time, keeping the devices clean and giving your ears periodic breaks to air out can make a meaningful difference.
Skin Conditions That Raise Your Risk
People with eczema or psoriasis affecting the ear canal or the bowl-shaped area of the outer ear are more prone to swimmer’s ear. These conditions cause the canal skin to become dry, flaky, and cracked, which weakens the physical barrier and creates openings for infection. The itching that accompanies these conditions also leads to scratching, compounding the damage.
Allergic reactions to hair products, jewelry, or earpiece materials can produce similar inflammation in the ear canal, thinning its defenses and setting the stage for bacterial overgrowth.
What Symptoms Feel Like
Swimmer’s ear typically starts with mild itching inside the ear canal, which is easy to dismiss. Within a day or two, the itching progresses to pain that worsens when you pull on your earlobe, press on the small flap of cartilage in front of the ear, or chew. The canal swells, and you may notice clear fluid draining from the ear.
As the infection advances, the pain intensifies and can become constant. The drainage may turn yellowish or greenish and develop an odor. The canal can swell shut enough to muffle your hearing on that side. Redness often spreads to the outer ear, and the lymph nodes near the jaw may become tender and swollen. Fever is uncommon in mild cases but can develop if the infection worsens significantly.
When Swimmer’s Ear Becomes Dangerous
In the vast majority of cases, swimmer’s ear is painful but not dangerous. It typically clears within 7 to 10 days with proper treatment. However, a rare complication called necrotizing otitis externa can develop when infection spreads from the ear canal into the surrounding bone and tissue. This is primarily a concern for older adults with diabetes or other conditions that suppress the immune system, as well as people undergoing chemotherapy or living with HIV. Men over 60 are affected most often.
The hallmark of this complication is severe, unrelenting ear pain, especially at night, that does not improve with standard ear drops. If pain escalates rather than improving after a few days of treatment, or if you develop facial weakness, persistent drainage, or fever alongside ear pain, those are signs that the infection may be spreading beyond the ear canal.
Keeping Water and Bacteria Out
Prevention comes down to keeping the ear canal dry and its natural defenses intact. Tilt your head to each side after swimming or showering to drain trapped water. A hair dryer on the lowest heat setting, held about a foot from the ear, can gently evaporate residual moisture. Over-the-counter drying drops containing a mix of rubbing alcohol and white vinegar help restore the canal’s acidity and speed evaporation.
Resist the urge to clean inside your ears with cotton swabs or any other tool. If you swim frequently, well-fitting waterproof earplugs designed for swimmers reduce water entry without trapping excessive moisture. And if you’re prone to recurring infections, keeping your ears dry becomes especially important during humid months, when CDC data show cases tend to peak.