How ear infections start
An ear infection happens when bacteria or a virus gets into the space behind your eardrum, called the middle ear. This usually begins with fluid buildup. The fluid gets trapped because the tube that normally drains it—the Eustachian tube—becomes blocked or swollen. When fluid sits there without draining, bacteria or viruses that are already in your nose or throat can move into that trapped fluid and multiply.
Most ear infections follow a cold, sinus infection, or sore throat. The same virus or bacteria that caused those infections can travel up the Eustachian tube. Anything that swells the tissues in your nose and throat—allergies, smoking exposure, or even sudden air pressure changes—can block that tube and trap fluid behind.
Key Takeaways
- Ear infections develop when the Eustachian tube (the drainage tube in your ear) becomes blocked, trapping fluid where bacteria or viruses can grow.
- Most ear infections follow a recent cold, sinus infection, or sore throat, because the same germs travel from your nose and throat into your ear.
- Children get ear infections more often than adults because their Eustachian tubes are smaller and more horizontal, making them easier to block.
- You cannot catch an ear infection from another person the way you catch a cold, but you can catch the cold or sinus infection that leads to one.
- Pain, fluid drainage, or hearing loss are signs the infection has started, and a doctor needs to examine your ear to confirm what is happening inside.
Why children get more ear infections than adults
Children under age 3 get ear infections far more often than older children and adults. The reason is physical: their Eustachian tubes are smaller, more horizontal, and still developing. That shape makes it easier for fluid to get stuck instead of draining out naturally. As children grow, their tubes become larger and angle downward, which helps fluid drain better.
Daycare attendance also raises the risk for young children. Being around other children means more exposure to the viruses and bacteria that cause colds and sinus infections—the triggers that lead to ear infections. A child who gets several colds in one winter is more likely to develop an ear infection from one of them.
The role of colds and upper respiratory infections
A cold or sinus infection is the most common setup for an ear infection. When you have a cold, the virus inflames the tissues in your nose and throat. That swelling extends to the opening of the Eustachian tube, narrowing it or blocking it completely. Fluid that would normally drain out gets stuck, and bacteria move in.
This is why ear infections often appear a few days after a cold starts to feel better. The cold itself may be improving, but the swelling in your nose and throat is still blocking drainage. The trapped fluid becomes a place where bacteria can grow unchecked. A sinus infection works the same way—the infection and swelling in your sinuses can block the Eustachian tube from the other direction.
Allergies, smoking, and other risk factors
Anything that swells the tissues in your nose and throat can block the Eustachian tube. Allergies cause that swelling, which is why people with untreated allergies get ear infections more often. Secondhand smoke does the same thing—it irritates the tissues and causes swelling that can trap fluid.
Bottle feeding while lying flat (rather than at an angle) can also increase ear infection risk in infants, because fluid can flow into the Eustachian tube more easily. Pacifier use beyond age 3 or 4 has been linked to more ear infections in some studies. Cleft palate or other conditions that affect how the Eustachian tube muscles work can make ear infections more likely throughout childhood.
What happens inside your ear during an infection
Once bacteria or a virus is growing in the trapped fluid, your immune system responds. The area becomes inflamed and swollen. Pressure builds up behind your eardrum, which is what causes the sharp pain many people feel. The eardrum itself may bulge outward from the pressure, and in some cases it can rupture, which is why you might see fluid or pus draining from your ear.
The infection can also affect your hearing temporarily. The fluid behind your eardrum dampens the vibrations that normally carry sound to the inner ear, so sounds seem muffled or distant. This hearing loss usually goes away once the infection clears and the fluid drains, but it is one reason doctors want to catch and treat ear infections—especially in children who are learning to talk and listen.
Signs that an ear infection is developing
Pain is the most obvious sign, but it is not always present. Some people, especially young children, show other signs first: tugging or pulling at the ear, fever, trouble sleeping, or acting unusually fussy or irritable. Fluid draining from the ear is a clear sign the eardrum has ruptured. Hearing loss or a feeling of fullness in the ear can also indicate an infection.
In infants and very young children, the signs can be subtle. A child might refuse to eat (because chewing and swallowing change pressure in the ear), have trouble balancing, or simply seem unwell without an obvious reason. If your child has had a cold in the past week and now shows any of these signs, a doctor should examine the ear to see what is happening inside.
When to see a doctor about ear pain
Ear pain that lasts more than a few hours, especially if it follows a cold or sinus infection, warrants a doctor visit. A doctor uses an otoscope—a small light with a magnifying lens—to look inside your ear and see whether fluid is present, whether the eardrum is inflamed or bulging, and whether there are signs of infection. This examination is the only way to know for certain whether you have an ear infection or something else causing the pain.
If you have fluid draining from your ear, fever above 102°F, severe pain, or hearing loss, seek care sooner rather than later. Children under 6 months old with any sign of ear infection should be seen by a doctor right away. Adults with ear pain and fever should also be evaluated, because while ear infections are less common in adults, they can sometimes indicate a more serious problem.
Frequently Asked Questions
Can you catch an ear infection from someone else?
You cannot catch an ear infection directly from another person. However, you can catch the cold or sinus infection that leads to an ear infection. If you are around someone with a cold, you might develop that cold, and then develop an ear infection as a complication. Washing your hands and avoiding touching your face helps reduce that risk.
Why do ear infections happen more often in winter?
Winter brings more colds and respiratory infections because people spend more time indoors in close contact with others. The viruses that cause colds spread more easily in that environment. Since colds are the main trigger for ear infections, more colds in winter means more ear infections. Dry indoor air from heating can also irritate nasal tissues and make blockages more likely.
Can you get an ear infection from water in your ear?
Water in your ear from swimming or showering does not cause a middle ear infection (the kind behind your eardrum). However, water trapped in the ear canal can sometimes lead to swimmer's ear, which is an infection of the outer ear canal itself. That is a different condition with different symptoms. Middle ear infections come from germs traveling up the Eustachian tube, not from water exposure.
Do all ear infections need antibiotics?
Not all ear infections are bacterial—some are caused by viruses, and antibiotics do not work against viruses. A doctor examines your ear and considers your age and symptoms to decide whether antibiotics are needed. Many ear infections in children resolve on their own within a few days, though pain relief and monitoring are still important. Your doctor will tell you what to expect and when to follow up.