The Essential Oil Desk Reference, 4th Edition tells us that “essential oils are lipid soluble and can penetrate cell membranes bringing an increase of 21% oxygen to the cells within 20 minutes of application.” [Source]
Ok, yes, they increase the oxygen supply and improve the blood circulation consequently and that is why more nutrients are delivered to the cells. It also improves the absorption capacity of the nutrients. Not only that, they are rich in anti-oxidants and can fight the free radicals. And, the EO’s can also prevent cancer. So, you see they are pretty much effective in their own way but then excess of everything is bad.