The Bioactivity of Essential Oils

This article explains how Oils have the ability to cross cell membranes and provide benefits directly to the cell.  This helps to overcome problems caused when the cell membrane transport mechanisms are suboptimal. 

Excerpt:

   Two features of essential oils enable them to be able to passively diffuse:

1. Lipid solubility
2. Small molecular size

   The cellular membrane is composed of lipids. Because essential oils are lipid soluble          and small, they have no problem crossing the membrane.

http://doterrascienceblog.com/bioactivity-of-essential-oils/