“Can you ingest certain essential oils?”

I do not recommend it. Many are toxic to nerves, liver and kidneys. Cinnamon essential oil is very toxic to the liver, when taken internally.
There are a few that are used therapeutically internally, but I do not suggest doing that without the guidance of a trained and certified health care provider, like a naturopathic physician. Stick with aromatherapy and topical (mixed with a carrier oil). If you want internal herbal medicine, make yourself some herbal tea and eat your vegetables (arguably herbal medicine too, right?)

I would not recommend this.

Not recommended