my grandmother has been using tea tree oil for almost 45 years. she uses it for literally everything from open cuts to cavity's in her teeth. it hasnt had any negative effects to her and shes almost 80. all it does is it helps keep infection out and helps things heal. i mean it wont heal a cavity it just delays the rot till you can see hte dentist next. she practically raised me on it. it doesnt taste good by any means. but ive seen it work.