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“I would never make or use a soap made with seed oils because we absorb them in our skin and seed oils are inflammatory.”
I’m not a scientist, but I prefer to refer to science-based publications when researching things I am not an expert in. Finding reputable sources for information in the cosmetics industry is challenging to say the least, and everyone has an opinion, usually not rooted in science or logic! This post is specifically in regards to SOAP, a wash off product, but some of the information does refer to leave on products as well, because it’s related and important information to consider!
What is soap? Soap is a sodium salt or potassium salt of long chain fatty acids having cleansing action in water.
Some things to consider when you are deciding what soap to lather up with:
Soap is a wash off product.
Soap is a salt, the result of a high heat, chemical process that transforms fats and sodium hydroxide into a new, completely different chemical compound. It is not necessarily the sum of its parts.
Our skin is our first line of defense, our physical, protective barrier to keep things out of our bodies and our blood stream.
Because you lather soap on and almost immediately rinse it off, whether the ingredients in it are touted to have amazing benefits, or alternatively, bad benefits, the fact it is a wash off product is going to severely limit any absorption, penetration, and benefit, even if the molecular structure is small enough to penetrate the dermis and epidermis and then be absorbed into our blood stream. It simply does not stay on our skin long enough to have much of an impact. More on that soon.
The chemical process that makes soap “soap” results in a bar that has very little “oil” left in it. Most soap makers use a super-fat of 5-7%, which means of all the oils and butters put in the pot in the beginning, only that % remains unsaponified in the finished bar. I cannot stress this enough - the saponification process chemically changes all the ingredients that go into the pot, and although we can hope the benefits of the raw additives and ingredients come through, there’s been very little scientific research into what actually survives. This goes for any purported bad benefits that may be associated with seed oils as well.
As an aside, let’s do the math on a 1,000 gram batch of oils, which would typically make 10 bars of cold processed soap in those Amazon molds. My hypothetical recipe has 20% canola (seed) oil and 5% super-fat left after saponification and cure. So, knowing 5% of the total oils are left, 200 grams was my canola, (1000g of oil x 20%), we have potentially 1000 x 5% x 20%, or 10 grams of canola oil unsaponified, across 10 bars of soap. So, we’re looking at about 1 gram of canola oil per soap bar.
For me, looking at the math, along with everything else I’ve researched, gives me a good perspective, and lets me form an educated opinion on how I think the seed oils will affect my body in a wash off product. Conclusions at the end!
I see people complain all the time about not using this or that because it is absorbed by the skin. I am here to tell you, maybe, sometimes, but not always. The ability of oils (or anything) to penetrate the skin depends on their molecular structure and size of the molecules. Oils that have smaller molecules and are less dense are more likely to penetrate the skin effectively.
Also, there is a difference between skin absorption and penetration. When a chemical penetrates the skin, it makes its way past the stratum corneum (the outer layer of skin) and into skin’s deeper layers. Absorption is when a chemical enters the bloodstream. You can see there’s a big difference.
With skincare, penetration is ideal. Ingredients will do their best work to hydrate and condition if they can get into the skin, but not leave the skin itself.
To refer to the point about seed oils being inflammatory, if you find topical application of anything irritating to your skin, don’t use it! However, please refer back to soap being a wash off product and a completely different chemical compound than its original components. But again, if it bothers you, of course don’t use it!
So, are we wondering if all ingredients eventually absorb? Since chemicals come in different sizes and have different absorption rates, not all of them are able to absorb into the body, or with enough speed to be effective, especially in a wash off product, like soap.
Wondering at what molecule size skin penetration is most likely? The 500 Dalton Rule is a good principle to understand. A Dalton is a unit of measurement roughly equivalent to 1 g/mol. Chemicals that absorb into skin through cells are generally under 500 Dalton. Both beneficial and irritating ingredients can have a molecule size less than 500 Dalton.
For reference, google says the molecular weight of canola oil is ~876.6 g/mol.
I found this great article, and I’m going to includes bits of it here. The article which has some great studies linked as well as those links are at the end of this article.
SO! There are three ways that chemicals enter into skin (please remember EVERYTHING is a chemical, e.v.e.r.y.t.h.i.n.g.):
Intercellular Absorption
Ingredients can absorb through the “glue” between cells of the stratum corneum. The intercellular lipid material is made up of ceramides, cholesterol, cholesterol esters, and fatty acids. The fact that it is oil based means that oils have a good chance of absorbing this way, while water based ingredients will be repelled since oil and water do not mix well.
Intracellular Absorption
The second route of absorption is through the dense, functionally dead cells of the outermost layer of skin, the Stratum Corneum. This layer of skin is 15 to 20 layers thick. Only very tiny molecules can absorb into skin this way.
Transappendageal Or Follicular Absorption
Compounds can enter skin through the openings that already exist in your skin as conduits between the lower and upper layers. Pores and hair follicles reach down past the upper layers of the epidermis and into the dermis where blood vessels nourish the skin. The pores and hair follicles represent only about .1% of the total surface of skin, so they are less likely to be the main avenues of skin absorption. However certain types of molecules may prefer the follicular route for skin absorption, so it depends on the type of compound in question.
Conclusion:
Personally, I wouldn’t choose canola or other cheap, highly processed seed oils in my leave on skin care products, as there are much better options for those products with amazing benefits. HOWEVER, as an ingredient in cold processed soap, a wash off product, along with other oils and butters, and properly formulated, that’s a definite yes. Looking at my example above, in an average 130g bad of soap and 1 gram of seed oil, that’s less than 0.8% seed oil. The key words here are “properly formulated”. I personally wouldn’t use more than 20% canola oil in a soap, and have decided all other seed oils are a no-go for me, except for high-oleic versions, based on the properties of the finished bar when I run scenarios through soapcalc.net.
Now, I’m not saying you should or should not use a soap made with seed oils, I’m just saying, if you do, it’s very different than slathering the raw oil on your skin and leaving it there, or eating it for that matter. Make a choice that aligns with science, as well as your personal moral, ethical and health requirements. There’s a lot of fear mongering and crunchy mommy blogs out there, and we need to sift through the nonsense and make the best decisions for us with the best scientific data we can find.
An article backed by some sciency links, and those links:
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