Saturday, November 6, 2010

Much maligned ingredients: Propylene glycol

In line at a shop the other day, a woman turned to me and told me that propylene glycol was in anti-freeze and ranch dressing! "I'm not eating anti-freeze," she said. I have no idea why she told me this. It wasn't like I was telling her about my love of cosmetic chemistry or holding a bottle of ranch dressing, but I think it's indicative of how people feel about this ingredient. So let's take a look at this much maligned humectant to see if it deserves this kind of derision!

Propylene glycol (aka 1,2-propanediol) is a polyol or poly-alcohol like glycerin. It's a clear, colourless, viscous liquid that tastes a little sweet (again, like glycerin). It can be used as an excellent humectant, a gelling agent in deodorant sticks, and a solubilizer of fragrances. It can be added to your surfactant based systems (like body washes and shampoos) to increase clarity (although it can reduce the viscosity), and it's added to our other products to act as an a freezing point lowering ingredient. It inhibits fermentation of products and it may be an effective fungicide and anti-microbial (although both of these things apply more to food than cosmetic products). It's edible, although you might find it has a bitter aftertaste. It's also a penetration enhancer, which means it can bring your actives into your skin a little easier than products that don't contain it.

Propylene glycol is a very effective humectant - possibly more effective than glycerin at certain humidities and temperatures - and this is why we see it in so many products. It's soluble in glycerin, water, and alcohol - so it's a water based ingredient we can add to our heated water phase of our products. Its suggested use is between 1% and 5%, although you can use it up to 50%. It can be an irritant at higher levels, so it's best to use it around 2% to 3%.

So what's with all the concern about this product?

Yes, it can be found in anti-freeze and ranch dressing and it serves the same purpose - all the glycols (including glycerin) reduce the freezing point of water (probably through disruption of hydrogen bonding), so that's a bonus for products that might end up being in the mail or a courier depot centre in Alaska for a while! There are many ingredients we use that can be found in other products, but being a possible inclusion in anti-freeze doesn't make propylene glycol a bad thing. (You could use glycerin in anti-freeze for the same purpose, but it isn't used that way because it would gunk up your car!)

It is a penetration enhancer, meaning it can bring things into your skin more easily than a product without it, and this is one of the reasons it is used in pharmaceutical ointments and unguents. If you want something to penetrate your skin, you need to do some work. Skin penetration isn't an easy thing - our skin is designed to keep stuff out, so we have to use some modifiers to get things through those layers. Adding a penetration enhancer can increase the efficacy of many of our ingredients - if they can get under our skin, they can moisturize from the inside out! A lot of things are penetration enhancers - urea, IPM, oleic acid, linoleic acid - and they don't get the same bad rap as propylene glycol.

Looking at some web sites I would normally avoid because they make me go ARGH, it is regularly noted that propylene glycol is an irritant. This is true. The CIR Review Panel has suggested it be used at levels lower than 50% due to potential irritation. And people with sensitive or damaged skin might find it irritating at lower levels. This is why there's the suggestion to use it at 1% to 5% in our products.

And it can be derived from petroleum, although there's a new product on the market, Zemea, which is derived from corn sugar. Zemea is much more expensive than conventional propylene glycol, but it has the same characteristics and is used in the same way.

I'm not trying to convince you to use propylene glycol - I just like to see what all the fuss is about and whether it is justified. In this case, I'm really not getting the hype! It seems like the same arguments could be made for glycerin (the anti-freeze part), IPM (the penetration enhancing part), just about any ingredient we use for irritancy, and many ingredients for the derived from petroleum part. 

Join me tomorrow for a look dipropylene glycol!

23 comments:

ukihunter said...

This is a great series, looking forward to the rest.

madpiano said...

brilliant article - once I am finishing my website, would you mind me linking to these?

Angela said...

lol I've heard that Anti-freeze comment before...
Thanks for posting the information. :)

Susan Barclay-Nichols said...

Hi madpiano! Let me know when your website is done so I can link back!

kontakt said...

Propylene glycol can be an irritant, yes. On the other hand it can also be found in pharmacies, in 50% solution (on perscription) or lotions with up to 20%, for treatment of eczema. As I understand it, some people are sensitive to it but for the rest of us, there's no problem.

Propylene glycol is not the holy grail for eczemas but some people's skin respond very well to it. I believe it's a combination of the hygroscopicity and the fact that it is slightly antiseptic - most eczemas are infected with bacteria or fungus - but I don't actually know. I add propylene glycol and urea to bought lotions and creams, it works well for me. I know someone else who makes her own lotions with 12-20% propylene glycol, for the same reason.

Blue Feather Soaps and Body Care said...

Have you found a supplier for Zemea? I would love to try it as an alternative.

Gillian

Anonymous said...

LOVE IT! Thank you, I've got it at home and didn't know what to do with it,,,, I feel safer lol

seventh77 said...

I've come across various "organic skin care" blog-type sites that claim propylene glycol "denatures" skin and causes it to age prematurely and sag. Is there any truth to that?

Susan Barclay-Nichols said...

Hi seventh77! I'm not sure what they mean by "denaturing" your skin. From Wikipedia: "If proteins in a living cell are denatured, this results in disruption of cell activity and possibly cell death." Do these sites mean this? If so, then they're wrong!

As for making skin age prematurely or sag - how do they explain that? Propylene glycol is a good humectant, and we know that humectants draw water to the skin, we know that humectants can reduce irritation, and we know that humectants reduce TEWL, so my thought is that propylene glycol should make our skin feel more hydrated and look less wrinkled!

erinwray2 said...

Has anyone found a supplier that sells this online, or anywhere in Canada?

Susan Barclay-Nichols said...

Hi Katie. Do you have a local feed store near you? I get mine from the farm supply store in my town. Check there!

Jillian said...

You can buy this at Ingredients to Die For. Their's is called Naturesilk (same INCI as Zemea); Naturesilk is EcoCert.

katt said...

hi there,, first i have to say i totally love your blog & site such great info I've also bought a few of your Ebooks,, so I have a small bath & body business I;m starting up & i get a lot of info from all over ,, recently I was in a soap group on FB & a woman asked me if i used propylene glycol at the time i had no clue what it was till i looked it up on your site,, besides the fact i dont use petroleum derived ingredients i dont see whats so bad about it so i asked her she went off on how it caused cancer & all sorts of stuff so i did some research & found a site called ATSDR which stands for agency for toxic substances & disease registry,, they say all it can cause is skin irritation depending on the person,, so my question is ,, is this a reputable site to get info from ??? it seems legit & basically coincides with what you say (I tend to trust what you say a lot)... I just want to make sure i understand all ingredients before i use them & need to know good site to get info from,, not a bunch of people who bad mouth products because they don't like them,,, thanks in advance for your time,,,
& again thank you so much for your amazing site,, id be lost without you lol

katt said...

oh I'm in canada so if you know any good sites to get legit info from that coincides with canadian laws that would be great too ,, thanks

Susan Barclay-Nichols said...

Hi Katt. I'm writing my response to your comment as today's Weekend Wonderings. The short answer is that it is a reputable agency! I don't know where to get Canadian specific information as I don't deal with business issues. (I'm also in Canada, BC to be specific...)

Kathleen Reid said...

Thank you ,, I know it's hard to find info agencies in canada seems everytging is done thru the states ,, thank you again

Anonymous said...

Great post!

I also like "the Curl Chemist" Tonya McKay´s take on the subject:

http://www.naturallycurly.com/curlreading/curl-products/curlchemist-the-truth-and-fiction-about-propylene-glycol/

Carol Blacklaws said...

Where can I buy Pentylene glycol - in the British Columbia lower mainland area? Does anybody know?

Blogger Susan Barclay-Nichols said...
Hi Katie. Do you have a local feed store near you? I get mine from the farm supply store in my town. Check there! (But there is no information to check).
December 7, 2013 at 7:57 AM

Anonymous Jillian said...
You can buy this at Ingredients to Die For. Their's is called Naturesilk (same INCI as Zemea); Naturesilk is EcoCert.

When I went to Ingredients to Die For (Austin Texas). It says:
NatureSilk is not Propylene Glycol, which is a petro chemical. NatureSilk is the plant based alternative to Propylene Glycol.
NatureSilk is 1 ,3-propanediol. Propylene Glycol is 1,2-propanediol.

Susan - So... any ideas as to where to buy Pentylene glycol in B.C.?

October 17, 2014 at 1:42 PM

Susan Barclay-Nichols said...

Hi Carol! Sorry, no. I've never seen this ingredient listed anywhere. Are you also looking for Zemea?
I know where to get hexylene glycol in the States. Why pentylene glycol? Just curious!

Carol Blacklaws said...

Susan,
I am looking for a distributor, store or somewhere in the lower mainland of BC that sells Pentylene glycol. I'm wanting to make a cream that has the following:

Water, olive oil, Coconut Oil, Shea butter, Vitamin E, Ceramide 3, Squaiane, Glycerin vegetable, Lecithin, Xanthan gum, Pentylene glycol, Sodium carboxymethyl betaglucan

My friend spends more than $100 for 44ml. of this cream from Germany. She is encouraging me to buy it;
If I made it for her I could show her that there is such as thing as "women's conned-cream".

Because of your wonderful site I am familiar with most ingredients except Pentylene glycol, Ceraminde 3 and Sodium carboxymethyl betaglucan. There isn't any info that I could find about these last ingredients on your site.
Carol

Susan Barclay-Nichols said...

Hi Carol. No, there isn't. I can't even find propylene glycol at a supply store. I have to go to a farm store for it! Why pentylene glycol? What does it bring to the product that you can't get from another humectant? I've tried hexylene glycol - from the Personal Formulator - and it's thinner than propylene glycol. Maybe there's something else that could be lighter than propylene glycol that would work as a good humectant.

That seems like a strange recipe. Its emulsifier is not complete. I don't believe this can work without another emulsifier. Unless there's a titch of oil - like 3% or so - and the lecithin might work.

Beta glucan is an ingredient I've discussed in the cosmeceuticals part of the blog. Take a look at it. It's very nice. I also talk about ceramides on the blog. Same section.

Sodium carboxymethyl is missing a word, which is "cellulose". It's a thickener. You can use all kinds of things in its place.

Wow, $100 for 44 ml. I'm definitely in the wrong business!

Good luck! And please let me know how it turns out! I love it when people share their experiences with others!

Christian Velasquez said...

Hello Susan I am formulating an anti grease shampoo but I can't decide if the humectant to use is propilen glycol or glycerine or if I can do both. This is because I am using high concentrations of surfactants so I need to clean the scalp an hair but I don't want to dry the scalp over time like it's happened before. Thank you. For the record I've been using 0.5% propilen glycol and 1% glycerin in the formula.

Susan Barclay-Nichols said...

Hi Christian. You can use either or both. I've written at length about humectants in the humectants section of the blog - look to the right hand side to see that link - so you can read more about all your options.

0.5% and 1% isn't much. Go for at least 3% to start! The nice thing is that glycerin actually makes for nicer bubbles, so you can go quite high without reducing the foam and lather!