Ear Infections in dogs can be simple, complex, multifaceted. Lots breeds predisposed. Dog ear is cone shaped going into the head. Any inflammation, discharge drains deep instead of draining out. It can range anywhere from a simple bacterial or fungal infection to a multifaceted infection involving breed predisposition, allergies, food allergies, trauma, environment, and probably as big PIA for Vet as owner. As general rule most OTC pet ear cleaning safe and ok to use. Apply, massage ear, then clean ear with paper towel over index finger, not Q tips. Food trial is one simplest trials for owner to do but take bout 30 days, and even if eliminate grains in foods have to do same with all treats. Couple more common foods to try fish/potato, duck/potato, lot time this helps but not 100% as lots time other allergy involved. Best bet is to consult your veterinarian, but realize this probably not a one and done. This post does not count as DVM consultation, just some advice from many years Vet.