The human ear is divided into three parts: outer ear, middle ear and inner ear.

Among them, the middle ear cavity has an eustachian tube connecting the middle ear and the nasopharynx. The end near the middle ear cavity is bone, which is usually open. The near nasal segment is cartilage, which can contract or expand. It is usually closed and only opened when swallowing, chewing, yawning or blowing your nose hard, which can adjust the pressure inside and outside the drum and has a drainage effect. Children's eustachian tube is shorter and straighter than adults, and its caliber is relatively larger. Therefore, when the nose or nasopharynx is infected (the common situation is a cold), it is more likely to suffer from otitis media than adults.

Most colds are viral, but after the onset, due to the decline of local resistance, pathogenic bacteria multiply, usually accompanied by bacterial infection.

Therefore, antiviral drugs are usually used in combination with antibiotics in hospitals.

There is also a relatively simple judgment method, that is, if the baby's runny nose is the same as clear water, it should be the possibility of virus infection, mainly using antiviral drugs; If the baby's runny nose is yellow-green, sticky and purulent, it is mainly bacterial infection and should be treated with antibiotics (the most common situation is that the runny nose is clear at the beginning of the disease, that is, it is mainly viral infection, and it becomes purulent when it gets better soon, combined with bacterial infection; But when it comes to runny nose, the cold is coming to an end.