Some kids have what is called "glue ear" where the eustachian tubes (what you "pop" when you go up in a plane, it equalizes the pressure on the ear drum) are narrow (most kids are narrow to start with, it's just something to grow out of)
combined with thick sticky mucous in the eustachian tube. That mucous happens as a result of allergies usually.
It is too thick and sticky to run down the eustachian tube, and out into the throat. Germs tend to grow in it because it's just sitting there, and so you get repeated ear infections.
sometimes the tonsils and adenoids block the tube, so the secretions can't get out. That happens when the T+A grow large due to repeated infections and allergic responses.
Things you can do:
Reduce allergens. The house dust mite population spikes in late fall right about now, and kids who are reacting to them often suffer ear infections for the above reasons as a result.
Here is the regimen I used: use a hepa filter vacuum, vacuum a couple times a week, don't let the kids sleep with stuffed toys, wash all bedding once a month, sleep on a rolled towel rather than a pillow or change the pillow every 6 weeks, encase the mattress in plastic, change or vacuum or wash your furnace filter once a month and consider changing to an electronic filter
AVOID SUGARS: sugar reduces the immune response to infection and makes a child more susceptible to infections. It also seems to help kids with recurring ear infections to avoid sugar in food and drinks. That includes honey and other "natural sugars".
I found a helpful book in Dr Leo Galland's Super Immunity for Kids. Great book for anyone whose kid seems to get infections easily or suffers allergies.
Drink more liquids and run a humidifier to help thin the secretions in the body all over. You will have to be sure the humidifier isn't growing molds, I've used a steamer type for years because my kids react to molds and most cold mist humidifiers make that worse. For asthmatics and mold sensitive people, a hot steamer is better.
Other things that MAY work: The ABC homeopathic remedy. THIS IS NOT A HERBAL REMEDY. People get confused between the two. HOMEOPATHICS AREN"T HERBS even if they are derived from them-- they are extremely small doses of sometimes poisonous substances that help the body overcome disease. Aconite 1 or 2 doses the first sign of ear pain and fever. Belladonna the next dose an hour later, Chamomile for the final dose the next morning.
Now a possible herbal that may help: Mullein. Get some, make a tea and give to the child to help thin the mucous. You can also steep some olive oil in mullein leaves, and drop warm oil in the ear.
I found those last two out, years after they would have done us some good. I mention them because I've heard they work, I don't know this from personal experiance.
Ds had about 9 sets of tubes in both ears. He has permanent hearing damage due to scarring on his drums. In spite of that he does fine. Lip reads well, doesn't need a hearing aid and runs the sound board at church.
When he was 2 he had one infection after another, at least once a month in the winters. When he was 3 the allergist we went to recommended tubes to prevent more hearing damage and so that he could learn to hear and speak properly.
Tubes can help. He was just a very allergic kid, with severe glue ear problems, and we had his tonsils out once, adenoids (which will regrow sometimes if the tonsils aren't removed with them) out twice. (second time I threw a hissy fit-- I'm an RN and knew my stuff, and made them take the tonsils out too, and that did help-- the adenoids didn't grow back for a third time).