If you are into natural skincare, you will have seen the statistics flying around the internet about 60% of your cosmetics ending up in your bloodstream. This urban myth keeps doing the rounds and people continue to believe it and share it. I wrote an article a while ago about this topic which showed that the chance of your cosmetics getting into your bloodstream depends on your skin, your immune system, your environment, the specific chemicals in your skincare and the way your cosmetics are formulated, so the answer is never going to be that simple.
I briefly touched on essential oils in that article, but I thought it would be good to look at their properties in a bit more detail and find out if and how they get into your bloodstream. I run Formula Botanica, the online Organic Cosmetic Science School, and this has been a topic of discussion in our fabulous student community there recently too. If you design natural skincare, this is definitely a scientific topic you should understand.
How does an essential oil get across the skin barrier?
Although aromatherapy is hugely popular and practiced widely all around the world, many people are not aware about how essential oils pass through the skin. Generally people understand that they can end up in your bloodstream, but the mechanisms by which this happens are frequently not described in articles and books when actually it is very interesting! (Keep in mind that I am a science geek so I will of course find this bit fascinating…)
As we know, the skin forms an awesome barrier between us and the world. It holds all our internal organs together (thank you skin!), keeps many chemicals out and forms a first defence against everything our environment throws at us. Nonetheless, it’s not impervious and many chemicals penetrate our skin to some degree. In the article I wrote last week titled “can your skin breathe?” we looked at certain carrier oils and saw that generally they don’t penetrate further than the top 2-3 cellular layers of the epidermis.
Essential oils are different because they have a much smaller molecular weight than carrier oils and therefore pass through the skin. When the molecular weight of an ingredient is under 500 Dalton (the standard measurement unit of atomic mass) then it is thought to be able to freely pass through the top layer of the skin, the stratum corneum. All essential oil components have molecular weights well under the 500 Dalton mark so they pass with relative ease.
The outer part of the skin, the epidermis, consists of different layers which are partly oil-loving (lipophilic) and partly water-loving (hydrophilic) which is why so many individual ingredients struggle to get past this barrier because they are generally one or the other and not both at the same time. However, essential oil constituents have an affinity with both oil and water (predominantly oil) which means that they find it easier to pass through the outer barrier of the skin.
Essential oils applied to the skin are exhaled
In 1940 a researcher called Straehli did some fascinating tests on essential oils. He found that all the oils tested appeared in his subjects’ breath following absorption through the skin (Tisserand & Balacs, 1995). In other words, the essential oils penetrate into the skin, make it into the bloodstream, diffuse all around the body to various organs including the lungs and are then breathed out. I bet you never thought you’d be exhaling lavender oil after applying your favourite skin cream!
Straehli found that different chemicals and their constituents were breathed out at different time intervals:
- 20-40 minutes – eugenol and linalool (these chemicals are components of many common essential oils including cinnamon and rose).
- 40-60 minutes – anise, bergamot and lemon.
- 60-80 minutes – citronella, lavender, geranium and pine needle.
- 100-120 minutes – coriander, peppermint and rue.
This study, and others that have been undertaken since then, show that essential oils certainly do make it into the bloodstream – and much further than that.
Initially an essential oil goes to areas of high blood flow such as skeletal muscle, the liver and kidneys. It may become absorbed into the fat tissue. However, it is thought that an essential oil does not stay in circulation for a long period of time. Eventually it is excreted through the kidneys in the urine, exhaled by the lungs, secreted through the skin or passed through in the faeces (Clarke, 2008).
Everyone’s skin and surroundings are different and every essential oil is different so clearly there are lots of different factors affecting absorption. Essential oils evaporate quickly when applied to warm skin so you will always find that a percentage disappears before it has the opportunity to penetrate the upper layers of your skin. However, warm surroundings enhance penetration of essential oils so a hot bath or a warm massage oil (or even warm hands!) increase the rate of penetration significantly, probably because of the increased blood flow caused by an increase in temperature.
Certain essential oils are more viscous than others (with absolutes – solvent-extracted essential oils – generally being most viscous of all) and this will also affect penetration – the more viscous, the slower the rate of penetration. Covering the skin with a non-permeable material will also significantly increase essential oil absorption into the bloodstream.
It’s all true… or is it?
So now you’ve read all of the above, you’re probably pretty convinced that essential oils end up in the bloodstream and other parts of the body, right? I found an interesting counter-theory online on a website called AromaMedical.org. I read this article on the misinformation of essential oil skin absorption with great interest.
The author is effectively saying that studies into the absorption of essential oils have never prevented test subjects from inhaling the oils during testing. His theory is that actually inhalation of essential oils leads to much faster absorption into the bloodstream and that generally most essential oils don’t penetrate into the skin.
It’s a fascinating theory and I’m sure he’s right about one thing – I bet most essential oil researchers haven’t made their subjects breathe through an alternative air supply while they had the oils applied to their skin.
I’m also sure that in some clinical studies it would be impossible to make subjects breathe through an alternative air supply because some researchers use fresh, healthy human skin (with no human attached!) to conduct their studies. Often this skin is taken from a person undergoing surgery, usually mastectomy or cosmetic breast surgery. The sample is then kept at normal skin temperature in a special chamber and the underside is continually bathed in a physiological solution to mimic the flow of blood and keep the skin and metabolically active.
This process allows researchers to look at the penetration of certain chemicals across the skin. Certainly one researcher at the University of London, using this process, found that the very outer layer of the skin (the stratum corneum) sometimes acts as a reservoir where some essential oil components can remain for many hours before they are released into the rest of the body.
While this inhalation-only theory remains untested (to my knowledge, please correct me in the comments below if you know more!), I think on balance it seems that essential oils do make it across the skin barrier and into the bloodstream. We also know that they are readily inhaled because of their volatility so if you use an essential oil you are likely to be inhaling it as well as absorbing it through your skin – both of these mechanisms will end up with essential oils in your bloodstream.
What’s in your skincare lotion?
Skincare manufacturers typically use between 1-5% essential oils in the cosmetics you buy. Here in the EU some safety assessors set strict upper limits for 1-2%, so the amount of essential oil you could be absorbing into your body is still tiny. If you buy a 100g lotion bottle which contains 2g essential oil then you’re clearly not going to apply all of it in one go, so with every application you’re only introducing a tiny amount of essential oils into your body.
If you are a DIY beauty home crafter or a professional skincare formulator, next time you are making a skincare potion or lotion which contains essential oils, give some more thought to the oils you’re using and the people to whom you want to sell. Essential oils are potent little chemical compounds and can help with a myriad of different skin and bodily problems.
Of course the cosmetics you’re making aren’t intended to end up in someone’s bloodstream, but as it appears they do then my advice is that you research the benefits and side effects of your ingredients fully so you understand what they might be doing to your customer.
Does it worry you that essential oils end up in your internal organs? Leave me a comment below!