As you may know, the blood brain barrier is the barrier membrane between the circulating blood and the brain. This membrane prevents certain damaging substances from reaching brain tissue and cerebrospinal fluid while allowing essential molecules to enter.
The blood-brain barrier is like a sieve or filter through which only molecules of a certain size or smaller can penetrate. The blood–brain barrier’s ability to severely restrict entry of all but small, non-polar compounds has made it difficult to access the brain and central nervous system directly.
The molecules of essential oils are so small that most of them can pass through the blood-brain barrier. It is interesting to note that these small molecules of essential oils make them so aromatic. The only way something can be aromatic is for the molecules to be so small that they readily leap from the surface of the substance and circulate in the air so they can enter our noses and be detected as odor and smell.
To better understand aromatic oils, you might consider that oils pressed from seeds, like corn, peanut, safflower, walnut, almond, olive, are not aromatic. Sure, they have a smell, but you can’t smell them across the room in minutes (or seconds) as you can when you open a bottle of peppermint or other essential oil.
Chemistry Plays a Role
The ability to cross the blood brain barrier is often attributed to the chemistry of the oils, specifically, those that fall into the class of “terpenes”, a family of molecules small enough to penetrate the blood-brain barrier.
Terpenes are a class of essential oils composed of “isoprene units” or organic compounds of five connected carbon atoms with some hydrogens attached. The terpene family includes Phenylpropanoids (only one isoprene unit), Monoterpenes (two isoprene units), Sesquiterpenes (three isoprene units), Diterpenes (four isoprene units), as well as Triterpenes (six isoprene units) and Tetrapenes (eight isoprene units).
Terpenes are found in most essential oils and are chemically credited with the ability to reprogram the DNA at a cellular level, in effect working as stem cells to correct bad cellular codes. Sesquiterpene molecules—commonly found in roots, resins and woods like Cedarwood, Vetiver, Spikenard, Sandalwood, Black Pepper, Patchouli, Myrrh, Ginger, Galbanum, and Frankincense—are also attributed with the capability of carrying oxygen into human tissue.