Acute otitis media
Infection of the middle ear that follows failure of the Eustachian tube to ventilate and drain it, so the same self-limiting process that causes glue ear can also cause a painful, bulging, infected drum.
First principles
The middle ear only stays healthy if the Eustachian tube keeps working
The middle ear is an air-filled cavity that depends entirely on the Eustachian tube to equalise pressure with the nasopharynx and drain secretions. In young children the tube is short, floppy and more horizontal than in adults, so it blocks easily, typically during or after a viral upper respiratory tract infection, when mucosal swelling closes the tube's narrow nasopharyngeal opening. Once the tube is blocked, the middle ear becomes a closed, negative-pressure space that fills with fluid, and nasopharyngeal bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis) can then ascend and multiply in that stagnant fluid, causing acute otitis media.
Educational content pending clinical review. Not medical advice.