Tuesday, April 3, 2012

Humectants: Other benefits

Humectants aren't just about drawing water from the atmosphere to our skin: Many of them have other effects that can benefit our skin. (Humectants are for hydrating; lipids are for moisturizing. See this post for more information!) For more about panthenol, click here. For more about glycerin, click here.

"A lipid-rich cream without any humectant had no influence on TEWL (transepidermal water loss)..." (Page 679, this paper). Think about this for a moment. A cream without a humectant had no effect on transepidermal water loss. Meaning that you could make yourself a decadent body butter filled with exotic and expensive oils, and it would not slow down the water loss from your skin. So you aren't really treating dry skin without using some humectant. Just 2% sodium lactate or 2% sodium PCA (and so on) could be enough to prevent the TEWL that leads to try skin. Ponder this...then think about how you're going to make changes in the workshop next time!

"Increased sensitivity to nickel was also found when nickel-sensitive humans treated their skin with moisturizers without humectant, compared to treatment with moisturizer with humectant. On the other hand, areas treated with the glycerol-containing cream showed less reactivity to nickel than those treated with a cream without any humectant." (Page 679, this paper.) So we can reduce our response to irritants by using humectants in our products?

"Treatments with SLS (sodium lauryl sulphate) solution under occlusion significantly increased TEWL and decreased skin hydration as assessed by capacitance measurements....Thus, irritant contact dermatitis treated with glycerol application compensate for skin dehydration, favouring physiological process to restore water barrier function of the impaired skin." (Abstract, this paper) In other words, it appears that using glycerin can reduce the TEWL caused by irritation.

Having said this, this paper notes that "Ten days treatment of normal skin with 20% glycerin significantly increased skin corneometer values, indicating an increased hydration. However, our study failed to show an influence of glycerin on human skin, in terms of TEWL and skin sensitivity to SLS-induced irritation." Mind you, this paper is from 2001 and the one above is from 2008, so there could be changes in technology or other experimental parameters that makes a newer study more valid. But we do need to take findings with a grain of salt when they go against other findings.

So it is possible that we can reduce our sensitivity to some ingredients or things when we use products that contain humectants. Or perhaps not. I don't see a downside to using humectants this way, although we never want to make claims of this nature, regardless of how much science we have to back it up!

If you want to know more on this topic, read this paper for more information. And click here for more information on stratum corneum lipids

"A pure liquid crystal system, produced by an all-unsaturated fatty acid mixture, allows a rapid water loss through the bilayers with a moderate barrier action. The solid system produced with an all-saturated fatty acid mixture causes an extreme water loss due to breaks in the solid crystal phase. Maintaining the balance between the two phases is required for optimal barrier function in preventing water loss...Prevention of SC lipids phase transition by glycerol has been shown. Application of 10% glycerol to a mixture of SC lipids in vitro inhibited the transition from liquid to solid crystalline phase, even if the water content in the media was reduced to 6%. As glycerol does not act as humectant at such a low humidity, the authors concluded that in a dry environment glycerol effects can be explained by influencing SC lipid phase transition." (Page 28, this paper).

In other words, it seems like glycerin keeps our lipids in a nice balance of liquid and solid, so we don't get too much water loss from either direction. So even in dry environments, glycerin is a good choice for our products as it keep our stratum corneum lipids in balance.

I think it's safe to say that there are reasons for using humectants that aren't about attracting water from the atmosphere, so those of us with really dry skin still have a good reason to include them in our products! So let's take a few days to see how we can incorporate humectants in products for all skin types, but especially dry skin!

Topical Use of Dexpanthenol in Skin Disorders, Am J Clin Dermatol 2002; 3 (6): 427-433
The clinical benefit of moisturizers, JEADV (2005), 19, 672-688
Skin hydration: a review on its molecular mechanisms (Journal of Cosmetic Dermatology, 6, 75-82)
Glycerol and the skin: holistic approach to its origins and functions (DOI 10.1111/j.1365-2133.2008.08643.x)

Effects of glycerol on human skin damaged by acute sodium lauryl sulphate treatment (click here)


Ruth said...

I am loving these last few days of information..
When It is done, I will be printing it out..to keep in my binder..
Thanks, Susan..

Nancy Liedel said...

LOVE YOU! LOVE THIS!! How's about a treatise on honey as a humectant?

I've been using it more and more.

Dawn said...

Susan, This has been just the info I needed for myself. I'm absorbing as much of this series as my brain will allow so I will also be printing it to go over and help me formulate. I have the dryest skin and I've learned so much as to why lotions never seem to be enough, which is why I started making my own. They are an improvement but I can see where this info will help me to use the appropriate amounts of the appropriate ingredients. Thanks!!

Patrick said...

Hi Susan,

I hope you can find time to look at this and offer some of your expertise. I'm 62 years old, have sun damaged skin, live in Alaska, and suffer badly from winter itch (xerosis). After finding very little relief from commercial skin-care products, and after following your blog for a few months, I am planning to make my own moisturizing body butter/lotion. Here is my proposed formula;

Lanolin 10
cocoa butter 5
Jojoba oil 4
soybean oil 5
bisabolol (~30-40% in German chamomile extract) 1
olive oil non-saponifiables 2
Emulsifying wax/ Polawax 6

Sum of oil phase 34

Water 45.5
Hydrovance (hydroxyethyl urea) 1
Urea 5
glycerin 5
sodium lactate 2
propylene glycol 2
allantoin 0.5
panthenol 2
glycolic acid 0.5

Sum of water phase 63.5

Germal Plus 0.5
bergamot oil 1
bay rum oil 1

Sum of cool down phase 2.5

Sum of all ingredients 100%

Your comments/questions/critiques are most welcome. I would like to know that I am not headed down the wrong track before I start this. Your advice is most appreciated.

Thanks and best regards

Lallam said...

Thanks for the references.

Maybe it is a weird coincidence but I spent the day reading on urea, glycerin and other humectants on Olionatura's blog (it's in German).

Susan Barclay-Nichols said...

Hi Patrick! I love seeing all those great humectants in your product for dry skin - everything I have been reading indicates that this is the number one thing you can do for dry skin (the second is to include an occlusive ingredient to trap in the water!). The only questions I have is about the amount of BHT - is that high or suggested? - and the amount of your emulsifier. If you're using Polawax, make sure it works out to 25% of your oil phase, which looks to be about 27%? If so, then crank that up to 7% and reduce your water by 1%. This looks to be a great recipe. Let me know how it works out for you! I really need to use more lanolin in my products!