OK, the PRESCRIPTION FOR NATURAL CURES by James F Balch, MD and Mark Stengler, ND, says:
Tea tree oil--
medicinal use: topically for skin fungus, burns, and acne, cold sores, mouth and gum infections, skin infections, vaginitis, warts.
potential side effects: too high of a concentration to the skin can be irritating. Use cautiously on the face. Do not ingest internally (except for mouthwashes), unless under the guidance of a doctor.
comments: it's excellent for athlete's foot.
I've used the mouthwash to help heal gum pockets and found it helpful.