Bacteria is the most common cause of dog ear infections, and requires a course of treatment to kill the species responsible for the infection. The most common bacteria involved in canine ear infections are: Staphylococcus, Pseudomonas, Escherichia, and Proteus.
A challenge to treating chronic yeast infections is identifying the underlying cause which is responsible for starting the inflammatory process which leads to infection by bacteria and yeast. Environmental allergies (atopic dermatitis) are believed to be the most common primary triggers for otitis externa.
Dog ear problems can occur in different regions of the ear. Otitis externa is the name for inflammation of the outer ear and ear canal. Otitis media is inflammation of the middle ear canal, and Otitis interna is inflammation of the inner ear. Both media and interna typically occur as a result of an untreated infection of the outer ear canal.
(In this RightPet section, we're focusing on treatments for the actual bacterial infection itself - and for supplements which boost the immune system. But if your dog is diagnosed as having environmental or food allergies, we have great sections for these conditions too.)