dxw
Well-Known Member
Excellent point. Anything you can smell is getting into your nasal passages and your lungs, and those moist membranous surfaces are far more absorptive than your skin.
I’m not sure that the skin was ‘designed’ for that purpose, although I agree that one function of our skin is to protect against entry into the body by dangerous things. However, the skin does absorb many many things.
Why, otherwise, would big-pharma makes local-application preparations for many anti-inflammatory drugs? Looking through the published literature you will find many examples of skin absorption, including volatile oils of the types that make up many essential oils. Of course there is also the tragic use of the VX nerve agent in Malaysia, not so long ago, to further attest to skin absorption. The skin is less permeable to the more recently used Novichok 5 … if anyone cares about such semantic differences.
Locally-relevant, to me at least, eucalyptus oil (containing lots of 1,8-Cineole) penetrates through the skin … a property than has been relied upon for many millennia … as do many terpenes (ti / tea tree oil) and linalool / linalyl acetate (lavender oil).
The outermost layer of the outermost layer of the outermost layer of our skin contains mostly ‘dead’ cells – that is the outermost layer of the stratum corneum, which is the outermost layer of the epidermis, which is the outermost layer of the skin. The cells that flake off are mostly dead but their living progenitors are not at all far away, 10 – 40µm away varying with the different parts of your body. That’s not a lot when you think that the epidermis, outer layer of the skin, can be 1.5mm thick.
So, yes, some of the outermost 15 – 20 layers of cells in your skin are ‘dead’ but that’s only a very thin layer and below that lies a very alive and very active organ.
Now the other aspect here is that ‘dead’ does not mean non-functioning, far from it. That ‘dead’ layer has, as suggested, some very important protective functions. Those squame cells may have extruded their nuclei and a heap of their other organelles but they’re
When the outermost surface skin cells, or squames, flake-off they are usually ‘dead’. So the outermost of the outer layer of the skin is mostly made up of ‘dead’ cells, linked together in a mostly lipid support matrix and containing a heap of keratin.
The lipid support matrix, important in keeping the squames in place and relatively compact, probably provides a clue as to why many oils seem to be absorbed through the skin … and mostly aqueous substances tend to be expelled.
They're oils and as such are not inclined to mix well with water. They prefer their own kind. They're hydrophobic although it's an awkward term to use when you think that molecules can't really fear or love anything.
Yes, and no. Many things are absorbed by the skin ... and some of them very rapidly (e.g. weaponized VX nerve agent). There is an awful lot of very good science showing, and quantifying, the skin absorption of things. Of course, given the structure of the skin, it should come as no surprise that lipid type stuff tends to be better absorbed through the skin than water type stuff.
If we'd evolved in an environment of lipid-rain I suspect the outer layers of our skin would be evolved to optimally resist lipid penetration.
What a dreadful image. Once I stopped chuckling I found myself agreeing completely. We live in an environment where water is the main liquid, and too much water is a bad thing, so it's no surprise that our integument has evolved with an outer layer that mostly repels water ... with the corollary consequence that drownings do not occur very often in showers.
A complex and 'charged' topic. Just my tuppence worth ... but I am currently planning not to use lavender or tea tree oil in any soaps I make for my sons, at least until I get a chance to read the latest high quality peer-reviewed published evidence.
