For most therapists diet is the method of choice to enjoy the essential oil in plants. We enjoy many herbs in cooking for their essential oils and fruits in desserts and drinks. Essential oil is however a convenient and very wide ranging substitute when the plants are not to hand for specific care purposes.
Yes we should not neglect the power of the humble onion. If you know
anyone who is losing a bit of 'go' then have then cut an onion into
thick rings in a couple of tablespoons of olive oil every day and add
that as a base to their evening meal. Only takes a couple of minutes to
cook up and most men can fry an egg. The weight will drop off them,
their appetite will be satisfied, and their boss, co-workers and spouse
will have all the 'go' they can handle!
We shouldnt neglect the unseen effects of the oils either for example
geraniol and d-limonene are listed as potential skin sensitisers but
both have potential value in detoxifying chemical carcinogens as they
increase the activity of glutathione S-Transferase (a detoxifying liver
enzyme) - in mice (Zheng et al 1993)