Many say not to use tea tree oil at all internally.

"Due to reports of severe side effects after tea tree oil ingestion, it is strongly recommended that tea tree oil not be taken by mouth. Although tea tree oil solution has been used as a mouthwash, it should not be swallowed. "

http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-teatreeoil.html


"Q. Can tea tree oil be ingested?
A. Tea tree oil (absolutly should not) be ingested orally "


http://www.teatreeoiluses.com/tea-tree-oil-uses-faq.htm