Sunday, April 19, 2009

Better crafting through chemistry: Humectants

If you'd like to know more about humectants, check out the humectants section of the blog where I go into far more detail than you see in this one post! 

Everybody doesn't like something, but everyone likes humectants - if they know what they are! Check out this lovely urea molecule - carbon (grey), nitrogen (blue), hydrogen (white), and oxygen (red), all coming together to make your skin feel lovely!

NOTE: You don't need to be a science geek (like me!) or a chemistry fan to enjoy this post. I put these little molecules on the site because they're so pretty!

Humectants are incredible things, and one of the essential components of skin moisturization (the others being emolliency and occlusiveness. Check out yesterday's post on your skin for more information).

I know I've written about humectants before (Humectants are a girl's best friend!) but I wanted to go more in depth with the topic. I mean, aren't you curious how these things work?

Humectants are hygroscopic, meaning they draw water from the atmosphere to an object. (Think about those packages of silica you get in every container shouting DO NOT EAT! These are humectants - we call them dessicants. They keep the food stuffs and computer components moisture free by drawing water to the little packet and away from the stuff you want to eat or use!)

They are hygroscopic because of the hydroxyl groups attached to the chain. This is a glycerin molecule - the hydroxyl groups are the OH groups representing bonded hydrogen and oxygen atoms. You might recognize OH from alcohol - the majority of humectants are poly-alcohols or polyols. The strength of the humectant is dependent upon on the ratio of hydroxyl groups to the carbon atoms. Glycerine has three carbons and three hydroxyl groups - a very nice ratio indeed!

Glycerin is the most common humectant you'll see for homemade bath & body products. We seem to use it in everything! It's a poly-alcohol or polyol, as indicated by the three hydroxyl (OH) groups on the molecule! It's an organic humectant - no, not organic as in certified, but organic in that it is made up of all "organic" molecules (as opposed to inorganic molecules, like rocks). It helps make bigger bubbles in our surfactant mixes, makes them a little more viscous, and it's inexpensive. It has a great ratio of hydroxyl groups to carbons (3:3), so it's very very effective as a humectant. Glycerin has been shown to accelerate the recovery of barrier function following damage to skin, and like the other humectants, it acts as an anti-freeze for the water in our products, lowering the freezing point and keeping surfactant mixes clear.

Glycerin does not wash off after hand washing, so it's a great addition to hand lotions and surfactant mixtures.

So if glycerin is so awesome a humectant, why would we consider other ones? Our bodies actually contain urea, sodium lactate, and sodium PCA, and each has a benefit. When we are considering the feeling of the lotion or creation, we have to consider that glycerin can be sticky at times, can make our creations more viscous (and we might not want that), and it can begin to draw water out of our skin in arid conditions.

I do love sodium lactate! It's inexpensive, easy to use, and doesn't leave any sticky residue in your products. It's a metal-organic humectant (the Na - sodium - is the metal part), as opposed to a poly-alcohol, like glycerin. It is found in our skin's natural moisturizing factor, and it's a very effective humectant. How effective? Very effective.

It has been found to improve the barrier properties of our skin (in studies, there is a decrease in the trans epidermal water loss, which is a good thing), it is believed to stimulate ceramide synthesis in the skin, and it increases the plasticity of our skin. It also acts as a mild AHA, which can help reduce "the look of fine lines and wrinkles".

It has a really high water holding capacity (meaning it's a very effective humectant), and it is about 1.5 times more effective in this department than glycerin.

So why not use it in everything? It can help treat acne and "signs of aging", and it's a very effective humectant. On the down side, it can make your skin sun sensitive, it can increase the rate of cell exfoliation (which is both good and bad), and it loses its efficacy when you've washed the area in question. So for something like a hand lotion, you're going to lose your humectant after the first hand washing! So great for body butters, foot lotions, moisturizers, toners, and other leave on products - not so great for products like body washes, hand lotions, or surfactant systems where you are going to be washing it away.

SODIUM PCA (salt of pyrrolidone carboxylic acid)
Again, this is found in your skin and it is a very effective humectant. Like sodium lactate, it is a metal-organic humectant (look at the Na or sodium atom) and it is 1.5 times more effective than glycerin and twice as effective as propylene glycol at drawing in water. It isn't sticky like glycerin, and it won't change the viscosity of your creations.

Again, why aren't we using this in everything? It's more expensive than all the other humectants (relatively speaking - it's about double the price of sodium lactate) and it can be washed off. So hand lotions and surfactant mixes are right out!

All these humectants are good at 1 to 5% in body care products and 2 to 5% in hair care products.

Because glycerin doesn't wash off, it should be your first choice in humectants for body washes, facial washes, shampoos, and hand lotions. Because they do wash off and you'll lose your humectant-y benefits, save the sodium lactate and sodium PCA for toners, body lotions, and anything that will stay on during the day. (It's great in hair care products, but not shampoos!)

Having said all of this, you can use whatever humectant you want in what you want - if you love glycerin, then use it in everything! If you want to use glycerin in lotions, use it! (I love it in lotions and body butters and creams and everything else!)

Click here for a really great brochure on formulating with glycerin and propylene glycol! 

We're going to be looking at urea in our Hydrovance post - coming up shortly - so let's move on to occlusive ingredients!

UPDATE: If you're worried about humectants drawing water from your skin in low humidity climates, worry no more! Check out this post - can glycerin draw water from your skin in low humidity climates?


Aesthete said...

Hi Susan, what's the maximum amount of glycerin you can add to a face cleanser before it's just wasted?

Susan Barclay-Nichols said...

This is a great question! I think the answer is - hmm. Glycerin is an excellent humectant that will stay on after you've rinsed your face, so you do want a nice amount in there. I tend to use 3% - why? I'm not really sure, to be honest. I remember reading once that this was the optimal amount...but I think you could go higher for very dry skin. I would think up to 5% would be a good thing.

Having said this, it can increase the bubble-age of your cleanser - which isn't necessarily a good thing for a facial cleanser - so I'm thinking 5% is a good amount for maximum humectancy and moisturizing.

Erica said...

HI Susan
What is the alternative to use from Butylene Glycol in my eye gel?

Susan Barclay-Nichols said...

Hi Erica. I don't know your recipe, so you'll have to experiment, but you can interchange most of the humectants for other humectants so you could use glycerin, honeyquat, or another glycol. I wouldn't use sodium lactate at over 2.5% as it can make you sun sensitive, but it would be good for anti-wrinkle type action (but it won't thicken like the other humectants). If you're using oils, you could use olive oil as it is a good humectant.

This is something that goes around your eye and not in it, right?

Aesthete said...

Hi Susan,
I was re-reading this post on humectants and was wondering if you've ever formulated with sorbital? It's described as having "excellent plasticizing & thickening effects providing viscosity & texture, stabilizes gels & provides good clarity, effective moisturizing properties, good smoothing & conditioning effects." It almost sounds too good to be true...I really value your opinion and if you have one on this ingredient, I would love to hear it. Thank you.

Susan Barclay-Nichols said...

Hi Aesthete. No, I haven't used it as I can't get it easily. It sounds like a great ingredient, and I've seen tons of recipes that include it. I think I'd like to write a post on this ingredient, so check in again tomorrow morning when I'll have time to put together what I've researched!

Susan Barclay-Nichols said...

Hi Aesthete. I've written up a post on sorbitol here. I hope this helps answer some of your questions!

Anonymous said...

Hi Susan,

I can never seem to get sodium lactate to disperse in water. It seems oily and just floats around in bubbles. This doesn't make sense to me since my sodium lactate (SL) says it's a mix of 60% SL and 40% water. So if I'm making a toner, I can't use SL since it won't disperse. Any ideas? Thanks

Susan Barclay-Nichols said...

Hi Anonymous. I have no idea why this might be. I just add my sodium lactate to the water phase of a number of different products and it's like it was never there it mixes in so quickly. Sorry I couldn't be more helpful.

Anonymous said...

Hi Susan,
Your reply on sodium lactate made me more curious as to why I was having such issues with it. I had a new bottle that I hadn't used yet and tried putting that into water. Well, it dissolved perfectly. So, obviously my first bottle of sodium lactate WASN'T sodium lactate and I have no idea what it is! Somewhat concerning since I've used it in facial moisturizers. I've emailed the supplier but I definitely won't be using it. Thanks again.

Magia said...


I live in the UK, and find it hard to get some of the ingredients you mentioned.

I am considering going for D-Panthenol, instead of glycerine, in the hope it will still stay on (I know it seems to cling to the hair when rinsed in conditioners), but be less sticky than glycerine.

My main use is for body butters and lotions.

What do you think of D-Panthenol? Is it any good?

I love your blog by the way! Some really helpful content!

Thanks, Magia

Susan Barclay-Nichols said...

Hi Magia! I love panthenol - see this post, and many others throughout the blog - and it's a great humectant to include in your products! I like to include another humectant with it - I'm a big fan of the humectants - and I use it in just about every product I make, despite the cost!

Tara said...

Hey Susan. I often have random moments where I'm left wonderg "WHY?". You once gave me advice about not using humectants on my fine oily hair, to avoid attracting unwanted moisture to it. BUT I live in a VERY dry climate (Edmonton, Alberta), so I was wondering if the humectants might actually pull moisture OUT of my hair (an attractive feature) and into the drier environment? What do you think....?

Susan Barclay-Nichols said...

Hi Tara. I'm always asking why this or why that, which is the sign of a very curious mind! This is a great question! The reason not to use humectants on your specific hair type is about the hair type, not the environment.

I've never been able to find definitive proof that humectants can draw water from our skin and hair into the environment, although you see people talking about that all the time. I have frizzy hair, and I'd love to be able to remove the water content from inside my hair to make it straighter, but alas...I can't make that happen! Plus, I don't want to dehydrate my hair - the water is what makes it elastic and helps it bounce back from damage.

Sorry I couldn't be more helpful!

seventh77 said...


Do you ever use *both* sodium PCA and sodium lactate together in one formula, or would you advise against that?

seventh77 said...

Also, I'm a little confused on the actual differences between sodium PCA and sodium lactate. In one of your posts you mentioned sodium lactate being a sun sensitizer at above 3% while sodium PCA is not; but are there any other differences? I stumbled across a site saying that sodium lactate is more powerful than sodium PCA and that it retains more water than sodium PCA. Is this true?

Also, what are the specific qualities each imparts to a formula? I've read that sodium lactate improves slip.

Alexis said...

Hi Susan,
You once posted a scale of hygroscopic abilities for humectants (sodium PCA > sodium lactate > glycerin > sorbitol). Can you also rank humectants on a scale of "tenacity"? I know glyercin is the most "sticky" and, conversely that sodium PCA and sodium lactate wash off easily. What about the others like sorbitol, panthenol, honeyquat, condition-eze, hydrovance? Is there a place on the MSDS where I would find this info? Many thanks!

Nedeia said...

Dear Susan,

I LOVE humectants. I always use glycerin, sodium lactate, panthenol, urea, Na PCA, oats and wheat proteins, I just LOVE them in my products! But I guess I tend to over use them, because sometimes the gels I ma using all of them into is sticky. I always use less than 2% glycerin, and I try to stay at 2% with all the other humectants.

So, my question is: how much is too much? Should I keep all humectants at a 3% or maybe 5% in my recipe , in order to avoid the stickyness?

I am an oily face girl, with blackheads and whiteheads and occasional blemishes, with a sensitive skin, and I LOVE experimenting in creating face gels. I usually use Na Carbomer to thicken them (I LOVE IT!!!), and I want to make sure I use all the goodies (aloe vera, chamomile hydrosol, algae extracts, proteins, humectants, niacinamide). But I have never managed to make a version that is sticky-free, so all my gels are now converted to post-razor blade treatments :). My legs love them , BTW.

So, I would very much appreciate your thoughts on that - maybe even a post on how sticky can humectants be, and what's a girl to do when she wants an overdose of humectants. Especially when we do not formulate bit (I rarely make more than 100ml of gel at a time, because it is hard to make accurate measurements even with a 0.01 g scale)

Great post, as always! what would I be without you? ;)

Nedeia said...

typing error :"when we do not formulate biG", not "biT :-)

Susan Barclay-Nichols said...

Hi Nedeia! I've just written a post on your question here - question: can we use too many humectants? The short answer is no, you can use what you like. The longer answer about reducing stickiness in your products - check out the post! Great question! Thanks for posing it!

Nedeia said...

Thanks :-)) Just 2 tiny typos in there, in my comment (if you could correct it in the post as well..): But I guess I tend to over use them, because sometimes the gel(S) I AM using all of them into is sticky.

Gel , not gels

I am, not I ma

Anonymous said...

here is the current link to the article you previously mentioned:

Anonymous said...

Anonymous: thank you for the current link! It helped me tremendously.

Swift: you rock. Your blog rocks. Much is still over my head, but I'm learning 'swiftly'. Thanks.

iconoclast said...

If the ratio of hydroxyls to carbons determines the efficacy of a humectant, then shouldn't sorbitol (6OH, 6C) be a better humectant than glycerin. What other factors come into play, since glycerine is a MUCH better humectant? Do you know of a comprehensive list comparing the hygroscopicities of various chemical compounds, including for non-cosmetic uses? Thanks.

Susan Barclay-Nichols said...

Hi iconoclast! I have a small table you can find in this post. The efficacy depends upon humidity, so it's hard to say that one thing is better than another without knowing those levels. This is, so far, the best chart I've found in all my materials.

As for your question, it's a good one. I don't know the answer to it off the top of my head, but it's going on the list for more research!

Sherra Murphy said...

This is such great information - my horse has very dry feet this summer and they've started to flake and crack a bit. The commercial preparation I'd normally use lists humectants, coconut oils and anti-bacterials as the main ingredients, and it costs a bomb! I'm off to concoct something with lovely oils and glycerine that I already have on hand, AND I'll know exactly what's in it. Thanks so much for this blog!!

Silvia said...

Hi Susan,
love your blog, live in Brasil and not easy to find information on cosmetics making here.
I make CP soap for 3 years now and started making some lotions and next step make hair conditioning and shampoo. Love my products, thanks to you!
The ingredients are not easy to find here though. I wisheed to make a lotion using sodium lactate, but can't find it here, just calcium lactate. Forgive my ignorance, but could it be used instead?Thank you!

Anna said...

Hi Susan,

Do you know which humectants except for glycerin doesn´t wash off? Hydrolyzed proteins? Hyaluronic acid? Different quats?

Thanks for an awesome blog!

Kind regards,

Susan Barclay-Nichols said...

HI Anna. Great question! I've answered in Sunday, September 14th's Weekend Wonderings. The short answer is that the only ones I know that wash off are sodium PCA and sodicum lactate.

Leah said...

Hi Susan,

I forgot to add my name and I just saw that posts without a name would be deleted - so sorry about that!

I am doing a science experiment. My experiment is on the best ingredient for a hand cream. Do you have any ideas on how this could be done? For example do you suggest I test 3 Humectants, and if so which 3. Or do you suggest testing one humectant, one occulsive and one emmollient?

Please respond with your ideas ASAP.

Thanks a million!!

- Leah

Anna said...

Hi Susan, I read the post where you answered the question about which humectants that doesn´t wash off. Thanks! :D

Susan Barclay-Nichols said...

Hi Leah. I have no idea what to suggest as I don't understand what you mean by your experiment. What does "best ingredient" mean? Best one for moisturizing? Best one for hydrating? Best one for soothing wind chapped skin? Best one for helping with acne? And so on. Can you be more clear as to what you mean by "best ingredient"?

Leah said...

Hi Susan,

To clarify, I want to test the for the best ingredient in hand cream that retains the most moisture. ( I will be helping my niece with this one for school using a jello mold for skin, and putting a membrane on top with homemade cream. We will then weigh the jello and see which jello mold lost the least amount of weight.)

How do you think its best to go about doing this? Alter the amount of humectants vs. occulsive vs. emmolient in the creams, test 3 different humectants, etc. It will be with homemade cream, nothing too complicated as she is in middle school.

Thanks so much, my neice and I really appreciate your wonderful blog and hints, she's your biggest fan ;)

Thanks, Leah

Susan Barclay-Nichols said...

Hi Leah. My suggestion is to do one that's all about occlusion, one that's all about humectants, and one that is a combination of the two. Make the only differences the occlusive/humectant ingredient. I would use your humectant at a good level - say 5% or so - and use your occlusive at a good level.

Which ingredients to use? From the occlusives, you can use dimethicone, allantoin, or cocoa butter. I would go with dimethicone or cocoa butter for more dramatic results. For the humectants, you could use a bunch of different ones, but glycerin would probably be the best bet!

Let us know your results! If you can send along some pictures, I would love to turn this into a post on the blog!

Leah said...

Hey Susan,

So we've been searching for humectants for the jello mold project, and the only ones we've been able to find are honey and glycerin. Do you have any tips of where to buy other humectants, or which ones we should be looking for?
Thanks so much!!


Michelle Squyars said...

Hello Susan,
I have read where soapers like to use sodium lactate in the HP and CP bars to harden them, however do you get any of the humectant properties if it is used in soap that is washed off?

Booboo Modest Maiden said...

My only concern with using Sodium Lactate is that it uses GMO beets and corn to make it. I am making my own soap and personal products to stay away from harmful chemicals. I wish could make my own or buy Non-GMO somewhere.

Benton Clay said...

FYI, The link to the brochure on formulating with glycerin and propylene glycol seems no longer to work.

SwiftyNoLonger (Merryweather) said...

Hi Susan,

Are there oil-soluble humectants?

Susan Barclay-Nichols said...

Hi SwiftyNoLonger! How are you doing? I don't go to the Dish forum much these days. Are you still around there?

Great question! I'm writing about it today in my Weekday Wonderings. The short answer is yes, there is at least one!

Supriya said...

Hi Susan
Since last few days I have been mixing 40 % of glycerine to my regular shampoo based on one of readers comment I think I read on surfactant he/ she said that her hair was soft after using glycerin with decyl glucoside kind of surfactant at 35% ,I could not make my own shampoo as I m still waiting for my ingredients but I could not resist myself n I tried with regular shampoo I must say my hair never felt this soft n manageable in my whole life n it reduced my frizzed hair up to 70% I have thin super frizzi and oily hair like if I wash my today with deep conditioner n leave in my hair wil be frizzi in abut 2 hrs ( with ur coconut oil conditioner and leave on spray which I was using earlier too ) so I am thankful to you and that readers of yours who made that comment I am sorry I don't know her/ his name but I hope they read it