Olive Oil--Effectiveness as Humectant vs. Glycerin
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Wed Feb 13, 2013 12:52 am

I've seen olive oil described many times online as a humectant. But I can't find any specific comparisons between olive oil and other commonly used humectants such as glycerin and sorbitol. Does anyone know how olive oil compares with these substances in terms of its effectiveness as a humectant? Thanks

Wed Feb 13, 2013 6:35 am

Not sure if you've seen this related article but it divides the moisturizing ingredients you listed above (as well as others) into three classes--occlusive, humectant, and reparative--with olive oil in the occlusive class:

http://www.futurederm.com/2012/05/09/what-are-the-differences-between-occlusive-humectant-and-reparative-moisturizers/

This textbook includes olive oil in with the occlusives and compares its ability to resist water vapor loss with petrolatum:

Occlusives: Oily compounds that can dissolve fats, occlusive agents are incorporated into skin care formulations in order to coat the SC and prevent TWEL. In addition to inhibiting TEWL, occlusives exhibit emollient properties, and are therefore appropriate products for treating dry skin. Petrolatum and mineral oil are thought to be the most effective occlusive ingredients. Used as a skin care product since 1872, petrolatum is also considered one of the best occlusive moisturizers, as well as the gold standard by which other occlusive agents are measured. Notably, petrolatum is thought to display a resistance to water vapor loss that is 170 times that of olive oil. Unfortunately, many consumers deem petrolatum to be cosmetically unacceptable because of its greasy texture. Other frequently used occlusive ingredients include paraffin, squalene, silicone derivatives (dimethicone, cyclomethicone), soybean oil, grapeseed oil, propylene glycol [functioning as both a humectant and occlusive agent], lanolin, lecithin, stearyl stearate, and beeswax.

Humectants: Humectants are hygroscopic, water-soluble substances. In conditions with at least 80% humidity, humectants applied to the skin exhibit the capacity to attract water from the external environment, as well as from the underlying skin layers, to the skin surface. In low-humidity conditions, however, humectants applied to the skin can absorb water from the deeper epidermis and dermis, thus contributing to TEWL and exacerbating xerosis. Combining humectants with occlusive products can help prevent such results.

http://books.google.ca/books?id=9-ALWZhXomAC&pg=PA933&dq=olive+oil+textbook+skin&hl=en&sa=X&ei=Kq4bUa2EK4qkiQK85YHYDQ&ved=0CDQQ6AEwAA#v=onepage&q=olive%20oil%20textbook%20skin&f=false

Glycerin:

It is important that a humectant agent when used as a moisturizer component be combined with an occlusive ingredient as application of a humectant alone can increase TEWL. For example, topical glycerin (glycerol) when applied alone to skin increases TEWL by 29%.

http://books.google.ca/books?id=feR61KKYPjkC&pg=PT315&dq=TEWL+by+29%25&hl=en&sa=X&ei=76wbUZK7FaS6iwK2hoCQDg&redir_esc=y

A potent humectant, glycerin has a hygroscopic capacity similar to that of NMF. In a 5-year study comparing high-glycerin moisturizers to 16 other popular moisturizers applied to 394 patients with severe xerosis, investigators found that the high-glycerin products were the most effective because they rapidly restored dry skin to normal hydration and their effects lasted longer than all the other moisturizers, including formulations containing petrolatum. As revealed by ultrastructural analysis of skin treated with high-glycerin preparations, glycerin expands the SC by augmenting corneocyte thickness an creating greater distance between corneocyte layers. Glycerin also stabilizes and hydrates cell membrances and the enzymes needed for desmosome degradation.

http://books.google.ca/books?id=hfpfAhW71OkC&pg=PA97&dq=glycerin+atlas&hl=en&sa=X&ei=va0bUfbELsj9igLCnIC4Aw&ved=0CDMQ6AEwAQ#v=onepage&q=glycerin%20atlas&f=false

Thu Feb 14, 2013 10:24 am

Thanks for the response. Yes, interestingly I've seen olive oil classified as an occlusive, a humectant, as well as an emollient. That's some good info on the occlusive properties.

Does anyone know any sources that describe olive oil's humectant properties, specifically as compared to other humectants like glycerin? Despite tons of online references to olive oil's humectant capabilities, I've yet to see a citation to a study.

free skin care · Thu Feb 14, 2013 7:53 pm

I have no clue where I read this, but there was a blog somewhere that said olive oil is more of humectant because it has more OH groups than other oils. (Does it? I don't even know.) Then I started looking around, and apparently it's the general consensus that o.o. is a great humectant. I'm pretty sure that theory is bunk-and-a-half because all triglycerides have that same glycerol backbone....and obviously oils don't suck up water like proper humectants do. If they did, we wouldn't need emulsifiers!

I think this rumor got started because olive oil soaps don't crack and dry out as easily as other soaps. That's the only thing I can guess, honestly. I racked my brain trying to figure this out for a good long while. I've got nothing.

I wanted to look into whether or not olive oil emulsions held water better than other types of emulsions, but I never really did because the whole thing just seemed silly to me. Even if they do, it's not the olive oil alone that's doing it.

free skin care · Fri Feb 15, 2013 8:03 pm

I have read claims of olive oil being a humectant (which I don't see how that's possible) and an occlusive (which I can understand). In any case I have been avoiding using olive oil on my skin after reading studies published on Pubmed that olive oil causes damage to the skin barrier. I guess under certain situations that might be of benefit because that might increase product penetration. I personally want my skin barrier healthy and intact as much as possible.

free skin care · Fri Feb 15, 2013 9:04 pm

SnowFairy wrote:

I have read claims of olive oil being a humectant (which I don't see how that's possible) and an occlusive (which I can understand). In any case I have been avoiding using olive oil on my skin after reading studies published on Pubmed that olive oil causes damage to the skin barrier. I guess under certain situations that might be of benefit because that might increase product penetration. I personally want my skin barrier healthy and intact as much as possible.

...and now that I think about it, if olive oil causes damage to the skin barrier, then it is not an occlusive either. I don't know what it is when it relates to skin, but I did not like the way my skin felt when I applied olive oil to it. Now, I have read studies that when taken internally, olive oil improves the skin (if there was a defficiency in EFA's to start with).

Sat Feb 16, 2013 10:25 am

Thanks guys

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