Adults get ear infections when bacteria, viruses, or fungi take hold in the ear canal or middle ear, usually after something disrupts the ear’s natural defenses. While ear infections are far more common in children, they still affect roughly 1.5 to 3.5 percent of adults each year, depending on age. The causes differ depending on whether the infection develops in the outer ear or behind the eardrum, and several everyday habits and health conditions raise your risk more than you might expect.
Middle Ear Infections and the Eustachian Tube
Most middle ear infections in adults start the same way: something causes the eustachian tube to swell shut. This narrow tube runs from the back of your nose to your middle ear, and its job is to drain fluid and equalize pressure. When a cold, sinus infection, or allergy flare-up inflames the tissue around it, the tube narrows or closes entirely. Fluid gets trapped behind the eardrum, and bacteria or viruses that were already present in the nose and throat migrate into that stagnant fluid and multiply.
The two bacteria most commonly responsible are Streptococcus pneumoniae and nontypeable Haemophilus influenzae. Cold viruses can also cause middle ear infections directly. The result is pressure, pain, muffled hearing, and sometimes fever. Adults have a structural advantage over children here: their eustachian tubes are longer, wider, and more angled, which makes drainage easier and infections less frequent. But when inflammation is severe enough, that advantage disappears.
Outer Ear Infections (Swimmer’s Ear)
Outer ear infections happen in the ear canal itself, the passage between the outside of your ear and the eardrum. Water is the most common trigger. When moisture sits in the canal for an extended period, it wears down the protective layer of earwax and skin that normally keeps bacteria out. The warm, damp environment that remains is ideal for bacterial and fungal growth.
Swimming is the classic cause, but showering, bathing, or even living in a humid climate can do it. You don’t need to submerge your head. Any consistent moisture that doesn’t dry out quickly enough can set the stage.
Everyday Habits That Raise Your Risk
Several things adults do regularly can make ear infections more likely:
- Using cotton swabs or other objects in your ears. Sticking anything into the ear canal, whether it’s a cotton swab, pen, bobby pin, or paper clip, can scratch the delicate skin lining the canal. Those micro-injuries give bacteria an entry point. Cotton swabs also push earwax deeper, which can trap moisture and block natural drainage.
- Wearing earbuds frequently. Earbuds themselves don’t cause infections, but they create a warm, enclosed environment that encourages bacterial growth. Poor earbud hygiene and sharing earbuds with others increase the risk of transferring germs. Earwax and moisture build up around the earbud tips, making the ear canal more hospitable to bacteria and fungi.
- Smoking or exposure to secondhand smoke. Inhaled smoke irritates the eustachian tube, causing swelling and obstruction. This interferes with the tube’s ability to equalize pressure and drain fluid from the middle ear, which leads directly to fluid buildup, pain, and infection. The effect applies to both smokers and people regularly exposed to cigarette smoke in their environment.
Allergies and Sinus Problems
Chronic allergies are one of the most overlooked causes of adult ear infections. When your nasal passages stay inflamed for weeks or months, that inflammation extends to the eustachian tube. The result is a condition called eustachian tube dysfunction, where the tube can’t open and close properly. You may notice a feeling of fullness in the ear, muffled hearing, or a sensation that your ears need to pop but won’t. Over time, this dysfunction traps enough fluid to create a breeding ground for infection.
Chronic sinusitis works through the same mechanism. Any condition that keeps the nasal passages and throat inflamed for extended periods puts pressure on the eustachian tube and raises the likelihood of a middle ear infection developing.
Health Conditions That Increase Vulnerability
Certain chronic health conditions make ear infections not only more likely but potentially more dangerous. Diabetes is one of the most significant risk factors. People with diabetes, particularly those with poorly controlled blood sugar, are vulnerable to a severe form of outer ear infection that can spread to the bone surrounding the ear canal. This aggressive infection is also a risk for people undergoing chemotherapy or living with a weakened immune system from any cause.
Skin conditions like eczema and psoriasis can also play a role. When these conditions affect the ear canal, they break down the skin barrier that normally protects against infection, making it easier for bacteria and fungi to gain a foothold.
How Common Are Adult Ear Infections?
Ear infections become significantly less common after childhood, but they’re far from rare. For adults between 15 and 24, the estimated annual incidence is around 3.1 to 3.5 percent. For those 25 and older, it drops to roughly 1.5 to 2.3 percent. A large study from the Netherlands found that incidence continued to decline with age: about 7.1 per 1,000 people annually for adults aged 15 to 39, dropping to 2.7 per 1,000 for those 64 and older.
In practical terms, if you’re getting recurrent ear infections as an adult, something specific is likely driving them, whether it’s chronic eustachian tube dysfunction, unmanaged allergies, regular water exposure, or an underlying health condition.
What Happens If an Ear Infection Goes Untreated
Most adult ear infections resolve on their own or with a course of antibiotics. But infections that linger or go completely untreated can spread beyond the ear. The most common complication is mastoiditis, an infection of the bone directly behind the ear. From there, the infection can potentially cause facial paralysis, partial or complete hearing loss, inner ear infection, or in rare but serious cases, meningitis or sepsis.
Persistent ear pain, drainage from the ear, hearing loss that doesn’t improve after a cold clears up, or fever alongside ear symptoms are all signs that the infection needs attention rather than watchful waiting.