Ear infections happen when bacteria, viruses, or fungi multiply in a part of the ear where they normally can’t thrive. The trigger is almost always something that traps fluid or disrupts the ear’s natural defenses. About 80% of children will have at least one ear infection, but adults get them too, and the way you get one depends on which part of the ear is involved.
Middle Ear Infections Start With Swelling
The most common type of ear infection occurs in the middle ear, the small air-filled space behind your eardrum. This space connects to the back of your throat through a narrow channel called the eustachian tube, which drains fluid and equalizes pressure. When that tube swells shut, fluid gets trapped in the middle ear with nowhere to go. Bacteria or viruses already present in the area begin multiplying in the stagnant fluid, and an infection develops.
The swelling that blocks the tube usually comes from something else you’re already dealing with. A cold, the flu, or allergies cause inflammation throughout your nose, throat, and ears. That inflammation narrows the eustachian tube enough to seal it off. This is why ear infections so often follow a few days behind a cold. You start feeling better from the virus, then notice ear pain, pressure, or muffled hearing as the trapped fluid becomes infected. Chronic acid reflux can also irritate the area enough to cause blockage.
The two bacteria most frequently responsible for middle ear infections are the same ones that commonly live in the nose and throat. Carrying these bacteria doesn’t guarantee an infection. The problem only starts when swelling traps them in the middle ear, giving them a warm, moist environment to grow in.
Why Children Get Far More Ear Infections
Young children are dramatically more prone to ear infections, and it comes down to anatomy. In small children, the eustachian tube is shorter, narrower, and sits at a nearly horizontal angle. That makes it easy to block and bad at draining. By around age five, the tube has grown longer, wider, and angled more steeply downward, so fluid drains out on its own more easily. This single anatomical change is the main reason ear infections drop off sharply as kids grow.
Children’s immune systems are also still learning to fight off the respiratory viruses that trigger the chain of events. More colds means more chances for the eustachian tube to swell shut. Kids in daycare or group settings, where viruses circulate constantly, tend to get ear infections more frequently.
Swimmer’s Ear Is a Different Infection
Outer ear infections, commonly called swimmer’s ear, develop in the ear canal itself rather than behind the eardrum. The cause is different too. Water that stays trapped in the ear canal after swimming, bathing, or showering creates a damp environment where bacteria and fungi can flourish. You don’t need to swim to get it. Anything that keeps the ear canal moist for extended periods can set the stage.
Your ear canal has a built-in defense system. Earwax is slightly acidic, which fights bacteria and fungus, and slightly oily, which creates a waterproof barrier on the skin. When that barrier breaks down, you’re vulnerable. Harsh cleaning, scratching the ear canal with fingernails or bobby pins, or skin conditions like eczema can all compromise the protective lining. Even very dry ear canal skin cracks enough to let bacteria in.
How Cotton Swabs Raise Your Risk
Pushing a cotton swab into your ear canal does two things that make infections more likely. First, it acts like a plunger, compacting earwax deeper into the canal where the body can’t sweep it out naturally. Impacted wax traps moisture and creates a breeding ground for bacteria. Second, the swab can scratch or scrape the delicate canal skin, breaking the protective barrier that normally keeps pathogens out. The ear canal is self-cleaning. Wax naturally migrates outward on its own, carrying debris with it. Inserting anything into the canal disrupts that process and increases infection risk.
Environmental Factors That Increase Risk
Secondhand smoke is one of the clearest environmental risk factors for ear infections in children. Kids whose parents smoke around them get more ear infections, carry fluid in their ears more often, and are more likely to need surgical ear tubes for drainage. Smoke irritates and inflames the tissues lining the eustachian tube, making blockages more frequent.
Allergies play a similar role. The mucosal swelling during an allergic episode affects the eustachian tube the same way a viral infection does. If you or your child have seasonal or year-round allergies, the repeated inflammation creates ongoing opportunities for fluid to get trapped. Managing allergy symptoms with appropriate treatment can reduce how often the tube swells shut.
Other factors that raise the odds include bottle-feeding while lying flat (which can allow fluid to pool near the eustachian tube opening in infants), frequent use of pacifiers, and spending time in crowded indoor environments where respiratory viruses spread easily.
What an Ear Infection Feels Like
Middle ear infections typically cause a deep, aching pain inside the ear, a feeling of fullness or pressure, and muffled hearing. You might notice fluid draining from the ear if the eardrum ruptures, which sounds alarming but often actually relieves the pressure and pain. In young children who can’t describe their symptoms, watch for tugging at the ear, unusual fussiness, trouble sleeping, or difficulty hearing quiet sounds.
Swimmer’s ear feels different. The pain is often sharp and gets worse when you pull on the outer ear or press on the small flap in front of the ear canal. The canal may feel itchy before it becomes painful, and you might see redness, swelling, or discharge. The pain tends to intensify over a day or two if untreated.
Reducing Your Chances
Since most middle ear infections follow respiratory illnesses, the most effective prevention is reducing your exposure to colds and flu. Regular handwashing, staying current on vaccinations (including the pneumococcal vaccine for children, which targets one of the main bacteria involved), and keeping kids home when they’re sick all help. Breastfeeding for at least the first six months provides antibodies that lower infection rates.
For swimmer’s ear, the strategy is keeping your ear canals dry. Tilt your head to each side after swimming or showering to let water drain out. A dry towel gently pressed to the outer ear helps. Some people use over-the-counter drying drops after swimming, which typically contain a mild alcohol solution that evaporates residual moisture. Avoid putting objects in your ears, including cotton swabs, and if you swim frequently, consider well-fitting earplugs designed to keep water out.