I read that many substances are toxic, it is all about body mass and dosage. That is why you read that 2-3 drops are harmless to humans.
I have used it for heartburn, stomach acid. It works immediately and the heartburn does not re-occur. I do not know how long you should wait until a repeat dosage if heartburn reoccurs but I have usually only needed to dose twice in 12 hours and then not again until the next occurence, (maybe years). It makes sense, TTO is an antibacterial and heartburn is thought to be caused by a bacteria called helicobacter pylori.
The first time I took it orally was about 5 years ago. I also take it if I have a painful stomach caused by trapped wind, again it makes sense that the trapped wind is caused by bacteria. I have also used it to treat diarrhea or suspected food poisoning (gastroenteritis -again a bacteria). Always 2-3 drops in a glass of water. As always if symptoms persist for 24 hours see a doctor!