I've taken Lemon EO quite a lot so far, i mainly stick to 10 drops of undiluted Lemon EO in a capsule taken once a day. It can take a few days (up to 10 days, once a day, daily) to build up in the body, but it has definite effects, even from the start.
It has Limonene which activates the Adenosine A2A receptor and i think has some interesting effects there as the A2A receptor interacts with Dopamine 2 and 3 receptors, Metabotropic Glutamate 5 receptors, and CB1 receptors. It also has Alpha-Pinene which inhibits Acetylcholinesterase and has some GABAergic properties. It works wonderfully for anxiety/stress, much preferred ime over something like Xanax so far.
It hasn't been Psychedelic for me, but when i smoke Cannabis i do notice a cleaner Cannabis high, and it feels like it makes the Cannabis more sativa-like (kinda like high grade Lemony strains) and reduces the Cannabis-related anxiety and paranoia and makes the headspace more enjoyable.
There are some rather noticeable tracers in certain light conditions, i've also seen tracers of stop signs a few times while driving at night.
I like how Lemon EO makes me physically feel, and definitely gives me a bit more of a stable and grounded headspace.
As for nausea/vomiting relief, early experiments with Lemon EO combined with Rue and Acacia seemed promising, but i need to investigate further, it did seem to do away with the nausea/vomiting, i think, but i took it usually either sometime right before the Rue or sometime right after, but it did seem to help.
And the Lemon EO also seemed to alter the Aya experience in a rather interesting but different way, something i think is worth more investigation, almost feels like Lemon EO does something with my sensory/perceptual center a bit, and is even a good bit noticeable with Cannabis. Lemon EO also seems to help a good bit with heartburn/gerd, as well as digestion, though i seem to get a bit of constipation (at 10 drops or more), and some diarrhea (8 drops, usually happens when you first start taking it and after a few days the diarrhea goes away), from it but that's pretty much the only undesirable side-effects i've noticed.
I've tried different dosages of Lemon EO but so far 6 to 10, possibly 12 drops, seems like a good dose, i would recommend a try, just make sure it's good quality oil, some brands are diluted or are not good quality, i get mine from a vendor on ebay and i've stuck with it for a couple years now, it's good oil. I've also tried Orange EO and Lime EO, but idk, they just don't resonate with me as much as Lemon, and so far Lemon seems much better than Orange or Lime.