If your dog is getting yeast infections, then it is a good idea to take a look at what you feed it, and see if that isn't part of the cause. Dog foods containing a lot of cheap grains like corn and wheat are common culprits, as are those containing lots of sugar (beet pulp, molasses) or yeasts.
Ditching that sort of cheap food if you're feeding it, and adding pro-biotics such as natural yoghurt (the sort with live bacterial cultures and no sugar) to the diet can help. In the case of yoghurt, it can also be applied topically.