it is very common, and extreemly curable.

Yeast grows in warm moist places. Dogs with log droopy ears are more supseptable than dogs with cropped ears. Certain breeds are also at a higher risk. Cocker spanials are one of those.

To treat it you just use the ointment and it will take care of the current yeast problem. In the future to help prevent it, clean your dogs ear occationaly with an ear cleaner solution (you can buy some at the pet store) and cotton balls. This will help keep ear mites to a minumum also. Just sqwirt a little into the ear canal, and gently rub it it, it should make a bit of a slurping sound and then use the cotton balls to clean it out.

Good luck!