Ear infection/irritation

Hi all, it’s my first post here. My 4 year old girl pocket bully has been suffering really bad with an ear infection in one ear that keeps reoccurring. I’ve put her on a raw diet encase it was anything in her kibble that could cause it. I have also had an allergy test for her but nothing major really showed up in it. Have already been to the vets who prescribed her tablets but they didn’t really help. Has anyone else had an issue like this and found any solutions? I’m UK btw if it makes any difference. Thanks