Ear infections in babies are primarily caused by bacteria or viruses that lead to inflammation and fluid buildup in the middle ear, the area behind the eardrum. This often happens after a baby has a cold, flu, or other upper respiratory infection, which causes swelling and congestion in the nasal passages, throat, and eustachian tubes-the narrow tubes that connect the middle ear to the back of the throat

. Several factors make babies particularly susceptible to ear infections:

• Their eustachian tubes are smaller, narrower, and more horizontal than in adults, making it harder for fluid to drain properly from the middle ear. This fluid can become trapped and infected

• Their immune systems are still developing, so they are less able to fight off infections effectively

• Swelling or infection of the adenoids, which are near the opening of the eustachian tubes, can block drainage and contribute to infections

Additional risk factors include bottle feeding (especially when lying down), exposure to secondhand smoke, attending group child care (which increases exposure to germs), seasonal allergies, and certain anatomical differences like cleft palate

. In summary, ear infections in babies are caused by bacteria or viruses entering the middle ear, often following a respiratory illness, combined with anatomical and immune system factors that make fluid drainage difficult and infections more likely