Wednesday, February 5, 2014

Can oils penetrate our skin?

Now that we've taken a look at the fatty acids and triglycerides we find in oils, let's see whether or not those things might penetrate our skin!

From this article: Skin Research & Technology. Aug2012, Vol. 18 Issue 3, p364-369. 5p. (Click here for the entire text)

Abstract: The aim of this study was the investigation of the penetration behaviour of four vegetable oils and of paraffin oil into the stratum corneum by laser scanning microscopy. In addition, the occlusion capacity of these substances was assessed by transepidermal water loss (TEWL) measurements. Petrolatum served as a positive control for skin occlusion. The study was conducted in vivo and included six healthy volunteers.

Results: Paraffin oil, as well as the vegetable oils, penetrated only into the first upper layers of the stratum corneum. TEWL measurements indicated that the application of the vegetable oils (except jojoba oil) as well as paraffin oil, led to a similar occlusion of the skin surface. The most effective occlusion was found for petrolatum.

Conclusion: For the investigated oils, a deeper penetration than into the first upper layers of the stratum corneum could be excluded. The decreased TEWL values indicate that the application of the oils leads to a semi-occlusion of the skin surface as it is intended by the use of oils to retain moisture in skin.

If you take a look through the study, you'll see that they used jojoba, soybean, avocado, almond, and mineral oils as well as petroleum. Soybean and almond oil penetreated the deepest, while jojoba, avocado, and paraffin oil penetrated only the first layers of our skin. (The overall penetration of our skin was quite low, only the top layers of our stratum corneum.) Interestingly, all the oils except jojoba oil reduced transepidermal water loss (TEWL) because of occlusion.

Let's take a look at another study and see what it says...

Citation: Journal of Dermatological Science. May2008, Vol. 50 Issue 2, p135-142. 8p.

Summary: Background: Topical application of oils and oil-based formulations is common practice in skin care for both adults and infants. Only limited knowledge however is available regarding skin penetration and occlusive potential of oils and common methods for measuring skin moisturization fall short when it comes to the moisturizing effect of oils. 

Objective: In this study we used in vivo confocal Raman microspectroscopy to test the efficacy of paraffin oil (mineral oil) and two vegetable oils in terms of skin penetration and occlusion. Petrolatum was used as a positive control. 

Methods: The products were applied topically on the forearms of nine volunteers and seven infants and Raman spectra were acquired before and at 30 and 90min following application. Depth concentration profiles for lipid and water were calculated from the Raman spectra. Skin occlusion was assessed from the amount of stratum corneum (SC) swelling measured from the water concentration profiles. 

Results: The paraffin oil and the vegetable oils penetrate the top layers of the SC with similar concentration profiles, a result that was confirmed both for adult and infant skin. The three oils tested demonstrated modest SC swelling (10–20%) compared to moderate swelling (40–60%) for petrolatum. 

Conclusion: These data indicate that there is no statistical difference between the paraffin oil and vegetable oils in terms of skin penetration and skin occlusion. The results for petrolatum show that in vivo confocal Raman microspectroscopy is sensitive and specific enough to measure both lipid uptake and skin occlusion events following topical application.

Again we see a result that says that the oils penetrate the top layers of the stratum corneum.

And from this book (page 261) we see that lanolin is able to penetrate the upper or superficial layers.

So I think it's safe to say that oils can penetrate the top layers of our stratum corneum...but does that mean anything? It's one thing to say that an oil can penetrate into our stratum corneum, but what does it do there? Are there any benefits to having an oil penetrate our skin?

Sure there are! The oils can help improve the barrier lipids found in our stratum corneum! They make up about 15% of the dry weight of the stratum corneum, and contain about 40% to 50% ceramides, 20% to 25% cholesterol, 15% to 25% fatty acids (those with C16 to C30 chain lengths, with C24 to C28 being the most common), and 5% to 10% cholesterol sulfate. The lipids are arranged in a highly organized lamellar arrangement (fine layers alternating between different materials) with small amounts of water present. This is considered to be a very effective barrier to trans-epidermal water loss (TEWL). Water trying to escape the through the stratum corneum would have to navigate a complicated maze through the bilayer and the corneocytes to get to the surface of your skin - so the lipids and corneocytes make this a much harder task!

Let's take a look at phytosterols and polyphenols tomorrow! 


Michelle Ulmer said...

Very interesting. I have little understanding of chemistry and am trying to follow this. Thank you Susan for bringing your scientific interest to this subject.

Anonymous said...

Yes,thanks Susan for all the time you put into researching to share with us and educate us.

Anonymous said...

Hello, I am looking for oils to make up a hot oil treatment for dandruff and itchy scalps. Would you be able to recommend any? I was thinking avocado and coconut.

By the way, keep up the good work. Your blog has really helped me.

Ebony Princess

Anonymous said...

Hi Susan, I am very confused by some research into Oleic Acid. (Experimental Dermatology, January 2014 While the language is well over my head, from what i can see, Oleic Acid disrupts the skin barrier and increases TEWL. So i guess this will lead to dry skin. I have also googled Oleic Acid and dry skin and keep finding comments about how it causes dry skin. I also read somewhere (sorry to be vague) that oleic acid in vegetable oil is esterified and bound and that is therefore ok. Phew, this can be very confusing! Please, please shed some light on this. Thanks as always, Rachel.

melian1 said...

"The oils can help improve the barrier lipids found in our stratum corneum! They make up about 15% of the dry weight of the stratum corneum, and contain about 40% to 50% ceramides, 20% to 25% cholesterol, 15% to 25% fatty acids" --so if we add ceramides and cholesterol to our lotion, it would actually be much better for dry skin? better than just oils, i mean, like olive or soy or whichever combo.

Anastasia Ionas said...

Plant extracts vs oils: why would you choose one over another?

Elysia Cryer said...

What about extra virgin coconut oil? I read that it's the only oil that can penetrate the hair shaft - is the same true for skin?

Anonymous said...

So what is the conclussion? I know its hard to be objective, as every body is different. But what oil would you use?

Anonymous said...

ignore my comment, found my answer in one of your other post. Have a lovely day, and please continue to educate us Mother of skin care. Greetings from Denmark.

Susan Barclay-Nichols said...

Hi Ebony Princess. Here's a link to a post on dandruff and I would think oils might not be a good idea for dandruff prone hair. Just my thought...

Hi Rachel. I have a post on this topic soon. I had written it to go with this series, but I wanted to add more research before I posted it. Look for it later this week- I hope.

Hi melian. Good question, and yes, if we could get a balance of those things in our products it would be ideal. This is why I like linoleic acid; it's a major component in ceramides. I think I need to write more about this topic!

Hi Anastasia. Good question...I'm answering it in today's Weekend Wonderings.

Hi Elysia. Take a look at this post on what oils can penetrate your hair shaft as there are quite a few that can penetrate. In fact, there's a bit of information there on how to figure out what might penetrate! As for oils penetrating our skin...check out the post!