Life Extension reported on the use of tea tree oil in eradicating yeast infection: "Studies found that the antifungal properties of tea tree oil lie in its ability to disrupt the yeast cell wall." If your dog is flopping its ears, shaking its head, rubbing its ears with its paws, scratching at its ears, or rubbing its ears on furniture and rugs, it may have an ear infection. Check for a pinkish brown residue inside. The colored residue is a symptom of a yeast or fungal infection. Tea tree oil, which comes from the Melaluca tree, has been proven effective in veterinary use for yeast and fungal infections.
Clean the ear. Use sterile gloves or very clean hands. Don't use cotton-tipped swabs; use special ear-cleansing pads (available at pet stores), cotton gauze or cotton balls. If you use cotton balls, be extremely careful not to leave bits of them in the ear.
Read the directions on the tea tree oil bottle. If the tea tree oil is pure essential oil, you'll need to dilute it with olive oil or water. Follow the directions on the bottle for dilution.
Place drops of the diluted tea tree oil into the base of the ear. (The dog will shake out any excess oil, so you might want to do this outside.) Massage the ear base to spread the oil throughout the ear and the canal; the entire base and canal should be coated. Treat the ears every six to eight hours during the day.
The number of drops you'll use will depend on the size of the dog. For a small dog, use three or four drops. Larger dogs will require more; you might, for example, use eight to ten for a Great Dane. The number will also vary depending on the size of drops your dropper bottle creates.
Treat the ears for at least ten days. If the yeast infection recurs or doesn't improve, check with your veterinarian immediately. It may be a sign of a lowered immune system or other problems.
Wash your hands after treatment.