So, let me start off by saying that I'm certainly not here to offend anyone's sensibilities, but there is a tremendous amount of FUD and misinformation in this thread about EO usage. In full disclosure, I work at KININ - we make blends using therapeutic grade essential oils, and I am one of a few people here who are in charge of both formulation and manufacturing process.
Let me see if I can answer the original question, which was 2 part:
What are they?
The way essential oils are made: Essential oils are another descriptor for botanical extracts. They are effectively full plant terpene extraction. Although it is certainly -possible- to end up with final product that contains actual oil (fatty lipids), this is extremely uncommon, and is specific to the botanical (plant) that you are extracting from. Essential oils are created using a few different common methods: steam distillation, co2 extraction, or cold press (less common).
Essential oils are not "oil."
Most essential oils do not contain fatty lipids, meaning that they are not (generally speaking) capable of causing lipid pneumonia, as they are not "oils" at all. In fact, when you see "natural ingredients" labels on some of your TFA or Capella, odds are these are in fact essential oils (heavily diluted)
To Tailland's point about harshness, this is a solid lesson in formulation using EO. Essential oils are the most concentrated form of terpenes available, so a TINY amount goes a long way, and getting your blends right is part science and part art. Literally a 1% difference in overall content changes the output of what you've built from highly therapeutic to straight expectorant.
Also, terpenes are very delicate, so if you're intending on vaping at sub-ohm, turn back NOW. It won't work.
Adding Bergamot
Great idea! We have a blend with Bergamot, Ylang Ylang, Frankincense etc, all of which are considered GRAS by FDA. Its one of the most popular blends we make. To be clear, I am encouraging you to experiment with concepts but you should be aware of a couple things:
1. The difference between just right and too much can be measured in microliters, so please be careful.
2. These are real plant extracts, so make sure you know what you're doing. I always like to use Eucalyptus as an example here. Narrow leaf Eucalyptus is generally safe, but Blue Gum Eucalyptus is potentially toxic.
Anyhow, enjoy responsibly, and remember, its just like everything else - safety first.
