Essential oils for internal usage

Hello,

My physician in Europe prescribed a mixed of essential oils that are diluted in oil and that I take orally twice a day. So far, I have been using the essential oils from UNDA but I have to order them from Europe and it is quite expensive...
Where can I find essential oils in the USA that I can use internaly - drink them (after they are diluted) as prescribed by my physician? Can I use any essential oils or do they have to have been made specifically for internal usage?

Thank you for your help,

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