Some basic ideas
Babies are prone to ear infection
because they have tiny plumbing that drains mucous made inside the ear to the throat.
That drain (eustacian tube) can be invaded by throat germs if it is not flowing. Exposure to cigarette smoke, perfumes, wood burning stoves, candles, cleaning fumes, etc. All increase chances the baby will have ear infections. Avoiding these helps, but growth is the main solution.