MAR 18, 2021 8 mins reading
What dermatologists won’t tell you about Facial Oil
Since 2015, Oil skincare products have become very popular among the celebrities and youtubers. Please let me explain deeper about oil products as a formulator/chemist
Since 2015, Oil skincare products started becoming a hit. And even the last generation women used oil to treat their skin commonly. Nowadays, many people still directly take olive oil from the kitchen and apply on their face. From my perspective, as a formulator/chemist, I would scream loudly: STOP, PLEASE!
Here, I am going to tell you more secrets that other bloggers or dermatologists haven't mentioned before.
WHY and WHEN do you need oil treatment?
Assort OIL into two major categories
Oil can be distinguished into two major categories, natural ones and artificial ones. I use the classification chart showed below to explain it.
Function of oil treatment
All of different kinds of oil only do one thing: to lock the water beneath the skin and fill out the crevices to protect the skin. What is Corneocytes? Let me explain the skin structure a bit here: Stratum Corneum is like a wall that has bricks, Corneocytes, and mortar, intercellular lipid. Crevices are the channels among all the Corneocytes. While the oil penetrates deeper, it will be less greasy and has less chance to clog the pores.
How to choose a good oil product?
A good oil won’t change the color and the smell through time before its expiration and doesn’t make you feel greasy or sticky, causing the pimples.
Why does oil change the color and odor?
Plant oil without anti-oxidants is the least stable oil because it has unsaturated fatty acid that can easily oxidize and go bad. Plant and animal oils are made of Triglycerides that can become unsaturated fatty acid with enzyme. Here you may ask: isn’t unsaturated fatty acid good for skin because it is natural anti-oxidant? This is correct. But don’t forget one thing: because our skin doesn’t have enzyme to transfer Triglycerides to unsaturated fatty acid, the oil can’t get through the stratum corneum with high molecule weight of Triglycerides. Therefore, it can’t deliver this unsaturated fatty acid into your skin. On the other hand, due to the unsaturated fatty acid, plant oil deteriorates easily. Once the oil deteriorates, it would cause the skin irritate. Among all the oil, high grade pure petroleum jelly is the most stable oil that won’t react with skin. This is the reason that many dermatologists recommend their patients Vaseline, which is one of pure paraffin relative products. Hence, getting benefit for skin from plant oil in terms of unsaturated fatty acid is challenging.
Crevices, the channels showed on the left graph called Intercellular, among Corneocytes are sometime narrow as 5 nanometers (nm), sometimes are wider, around 70 nm. The average size of this crevice is 50 nm. Hence, the ingredients that are smaller than 5 nm can penetrate into skin.
Image credited: Clinical Gate
Why does oil make you feel greasy and cause pimples?
While the molecular weight of Salicylic Acid is 138 kg/mol, its molecular size is around 1 nm. As compare to the molecular size of Salicylic Acid in terms of molecular weight, 50 nm non-liner element has the molecular weight smaller than 500 kg/mol. In conclusion, the ingredients that have molecular weight smaller than 500 kg/mole can permeate into skin through intercellular channels. (This is what you need to remember.) The smaller size oil is, the deeper it can permeate. Now, a question for you, do you think animal oil is bigger size, or plant oil is bigger size? They are the same! Both plant and animal oils are made of Triglycerides. But Jojoba oil is the exception. Its chemical structure is more like wax ester and its molecular weight is around 600. To sum up, plant oil and animal oil are equally big, having similar size molecules.
How deep can these different types of oils sink into our skin? Here is the answer (The different colors demonstrate different oil penetration levels):
Olive oil, Coconut oil, and Jojoba oil have the molecular weight more than 500 kg/mol, which means their molecule sizes are bigger than 5 nm. These oils can only stay on the first layer of stratum corneum. Therefore, you can feel them vividly after you apply on skin. More important is that you have high possibility to get pimples if you continuously use them.
Squalane molecular weight is smaller than 500 kg/mol. Accordingly, its molecular size is smaller than 5 nm and can pass certain layers of stratum corneum. Because it’s small size molecule, it won’t clog the pore. Squalane is the product of Squalene after hydrogenation. In our skin, Squalene exists among intercellular lipids. Because Squalane and Squalene are very similar, Squalane is more affinity to skin than any others.
Paraffin is complex compound that has varied molecules. Paraffinum liquidum or mineral oil has average molecule weight between 150~282 kg/mol. Vaseline, called petroleum, has slightly bigger average molecule weight between 350~600 kg/mol and been used commonly in many baby’s products or even medical balms. Paraffin is non-ionic and doesn’t have any reaction with skin cells and only does one thing on the skin, which is to seal the skin and to prevent water loss. Many people stigmatize paraffin that causes eczema or allergy. From chemistry perspective, only impurities, like Benzene, in paraffin cause these problems. High grade paraffin that has been purified and refined is usually considered as the most stable and safe ingredient. However, if the skincare products are not OTC or medical grade, they often are made of lower grade industrial paraffin that has many impurities. High grade paraffin is usually very costly.
Isopropyl myristate (IMP) has very small molecules and can permeate deeper, but it doesn’t have any skin benefits and stays under the skin forever. This synthetic ester cause pimples after long-term usage. Of course, artificial oils / esters are not all that bad to skin. Many of them are good and won’t cause allergy, neither pimples, like Cetyl Ricinoleate, Isononyl isononanoate, Isotridecyl isononanoate…
I hope you enjoy this long article and can understand more about OIL, being a smart consumer. Again, before buying the oil products, listen to your skin first. If you have dryness, itchiness, peeling, and redness, you may consider to get a good oil for yourself by following what I explained above. Leave the comments below to let me know if you have further questions!