Pure theraputic grade essential oils are the only ones that I have found to be safe for internal use.
The EODR is the bible of essential oil therapy and can highlight most every subject related to pure oils. Which oils that can be used for internal use are listed and the basic guidelines can be found on page #27
"Essential Oils Desk reference" isbn 0-943685-39-7 http://www.essentialscience.net
If you humbly request a copy from your library, they may orer a copy. The New York Main Queens library was so impressed when I showed them the "EODR" book they are placing an order.
There are good essential oils from many companies. So far the best, most accessable, and easily duplicatable that I have found are from http://www.YoungLiving.com . If you enter code # 407126 and place an order for the success kit, item number code # 3160, costs about 50$ us currency AND you can get all items at approx %24 discount or whole sale price. Everything there is natural, even EI or MCS people can use these products once they have gone through a transition period.
God Bless, Nitai Gaura Haribol
PS At http://www.PureBhakti.com you can download free yoga books. So great are these teachings that courses are being offered at major universities around the world, including Oxford, Yale, Berkeley. Just remember that academic knowledge of these sublime teachings is entirely different from experienceing them.
PPS Actor Steven Seagal uses Young Living oils and he regularly goes to hospitals to anoint people.