<s>[INST] How Do Ear Infections Happen? [/INST] A middle ear infection usually happens because of swelling in one or both of the eustachian tubes (which connect the middle ear to the back of the throat). The tubes let mucus drain from the middle ear into the throat.

A cold, throat infection, acid reflux, or allergies can make the eustachian tubes swell. This blocks the mucus from draining. Then, viruses or bacteria grow in the mucus and make pus, which builds up in the middle ear.

When doctors refer to an ear infection, they usually mean otitis media rather than swimmer's ear (or otitis externa). Otitis media with effusion is when noninfected fluid builds up in the ear. It might not cause symptoms, but in some kids, the fluid creates a sensation of ear fullness or "popping." Source: KIDS HEALTH ORG. Link: https://kidshealth.org/en/parents/otitis-media.html. Field: Otolaryngology. Disease: Ear Infection </s>