It could be that his ear canal is shaped in a way that makes him prone to ear infections. If he was younger, you may have been able to consider an ear canal ablation. Some members have done this and had good luck with it.

If there is a tumor present, I suppose that could cause stuff to get stuck in there and create a breeding ground for bacteria. Did they say what kind of tumor? Usually when you think of a “tumor” in the ear, you think of papillomas. Abscesses are also possible. Tumors, as in cancerous growths, are less common but still possible.

Do you know if his ear drum is ruptured? If not, you could try an antibiotic directly in the ear. Sometimes antibiotics have a hard time reaching the ear when they are administered orally. Several members have had luck with ear drops with a non-ototoxic antibiotic. Steroids are best avoided, but they are less harmful in the form of eye drops or ear ointment.

Are you sure bacteria is what is causing the problem? Ear infections can be caused by yeast too.

Hmm… I don’t think so. At least not necessarily. Bacteria and yeast have different culture requirements. It also takes a long time to culture yeast. Someone can correct me if I’m wrong. LOL

If the swelling is really bad, you could try a steroid ointment to help get it down. It usually doesn’t take much. Like I said, steroids are best avoided in rabbits but they are less harmful in eye drop or ear drop/ointment form. I mean, all steroids are bad… this is just less bad if that makes sense. I don’t want people to get the wrong idea. Anyway, I have used both (very short duration, of course) in the past and they were prescribed by a vet.

There are a few antibiotics specifically known for ototoxicity. Just something to be aware of. I have actually had luck in the past with Enrofloxacin (Baytril) in the form of “antibiotic earwash”. But if his eardrum is ruptured, then you wouldn’t be able to use antibiotics directly in the ear anyway.