Just as an addition to this... MH has stated before that there are a lot of companies that sell various grades of oregano oil. He doesn't generally know who sells the good quality and who sells the dregs. See these posts of his:
Some are hardly even fit for consumption, so that is part of his warning. The good oils are generally clear and a moderate amber color.
It is recommended to take the oil, if full strength a drop in an empty capsule. Another way is a drop to a gallon of distilled water. Taken directly it certainly burns quite a bit.
Finally, MH has stated that Dr. Cass' "Super Strength" contains only 1 part oregano to 11 parts olive oil. Diluted this way is how we usually take it, and it doesn't have the burn when directly used in the mouth or even close to when mixed in a small glass of water.