My son has had repetitive ear infections and last month had to get tubes in his ears but still has ear infections. what can cause this?

Ear infections: Chronic eustachian tube disease. If attending daycare, URIs and poor hygiene between kids is common. Should be able to get matters under control with oral antibiotics and topical Abx ear drops. May need CT scan of mastoid. If still taking bottles, make certain head is elevated. No bottle propping. Keep water and shampoos out of ears

The basics: The walls of the middle ears make mucus like most membranes in the head/upper airway. Normally this drains down the Eustachian tubes into the throat. Infants/toddlers & some others have tubes that swell shut with colds/allergy/etc. & the retained mucus becomes food for germs. PE tubes bypass the swollen tubes but mucus remains that can be infected. Tubes usually drop infection frequency by 80-90%