Monday, June 24, 2013

Hygral fatigue and coconut oil (heavily edited)

Someone mentioned the concept of hygral fatigue in a comment the other day, and I thought I'd share what I've learned! It's a term used to describe the constant swelling and contracting of the hair shaft by water caused washing too frequently (or possibly absorbing water from the atmosphere).

Point of interest: I've amended this post like silly to reflect the studies I've been reading over the last few days. The information might seem a bit disjointed because I wanted to amend it as soon as I can. I'll edit for readability later this week. 

It seems to me that a lot of the information on the 'net about hygral fatigue and oils good for our hair is based on one study - this one - that has been referenced by many many sites I've read. I think the references you see on most sites are references to a blog post by the Beauty Brains rather than the actual study. The Beauty Brains wrote a post on the study, then added an amendment to note that they were discussing oils based on another study, not this one. This study only looked at mineral oil and coconut oil. The Beauty Brains mention meadowfoam seed, olive, sunflower, avocado, and jojoba oil, but amend their post to note these other oils are from a different study, not the one linked above. I'm also basing this belief of this study being the basis for these blog posts because there are two things in it I've never seen before - the idea of coconut oil being polar and the mention of the term "hygral fatigue". 

There's no doubt that water in the hair shaft might not be our friend - swelling causes friction and friction causes damage - and there's no doubt that our hair can stretch up to 30% when wet, so we must be very careful when brushing or combing in that state, but I have never seen the term "hygral fatigue" used in a textbook, paper, or study or by a cosmetic chemist. In all the years I've been studying hair care stuff, I saw it the first time this week by a commenter writing about the Curly Girl technique.

Correction: I found it in this study, the only place I've seen this term.

The cure for hygral fatigue seems to be pre-washing or post-washing with coconut or mineral oil, both of which are touted as being polar. Part of this is true. If you coat your hair in any oil, you'll keep out water as it forms an occlusive layer. This coating feature is not unique to coconut oil - any oil can perform this function - and these oils aren't polar.

This is one of the reasons those of us with frizzy hair concerns use cyclomethicone and dimethicone - they keep the water out and keep our hair smooth. It's also the reason they're used as heat protecting products - they keep the water we have in our hair from escaping! 

Coconut oil is not a polar oil. No natural oils are polar. (I will be writing more about this later this week...) Mineral oil isn't polar. To be polar, a molecule has one end that is more negatively charged and one end that is more positively charged. This is a result of the electronegativity of the atoms involved in the bonding. The larger the difference between the electronegativities of the atoms, the more polar the molecule. If the polarization gets too much, it becomes an ionic bond. Coconut oil and other oils, are considered non-polar.

Polar things tend to mix with polar things, which means a polar coconut oil should be able to mix with water without the help of an emulsifier. It doesn't. (This isn't coconut oil - I think it's sunflower, but the point remains the same!)

Edited to add: I know that study says coconut oil is polar, but I'm confused by this. Oils are generally held as being non-polar, so calling this oil polar is very strange. I realize Yahoo answers isn't a scholarly resource, but here's a description why coconut oil isn't polar, which I quote to demonstrate that the non-polarity of coconut oil is an accepted thing. Here's a site from Elmhurst University about the non-polarity of oils. But then I found this study that said, "Coconut oil has shorter alkyl side chains than SBO and therefore has a higher polarity and lower molar volume." But this is a comparison with soy bean oil, so it's more polar than soy bean oil...but what does that mean? The thing is that polarity is a continuum, not an either/or situation. So it can be more polar than soy bean oil, but not be considered polar. Then I found this review about coconut oil that stated that, "Medium chain triglycerides are widely used in the flavor industries as they are more polar and therefore more hydrophilic and can dissolve a variety of polar substances that are insoluble in conventional fats and oils." But this is about the triglycerides, not coconut oil. I'm investigating this further...

Edited: I really recommend you check out this post for the studies I've found about oils and hair penetration.

It appears that coconut oil can penetrate the hair strand into the outer cortex! See the studies and the conclusions in this post for more information. Its fatty acids seem to have an affinity for the protein on our strands. This study is the one everyone quotes, which notes...
coconut oil was the only oil found to reduce the protein loss remarkably for both undamaged and damaged hair when used as a pre-wash and post-wash grooming product. Both sunflower and mineral oils do not help at all in reducing the protein loss from hair. This difference in results could arise from the composition of each of these oils. Coconut oil, being a triglyceride of lauric acid (principal fatty acid), has a high affinity for hair proteins and, because of its low molecular weight and straight linear chain, is able to penetrate inside the hair shaft. Mineral oil, being a hydrocarbon, has no affinity for proteins and therefore is not able to penetrate and yield better results. In the case of sunflower oil, although it is a triglyceride of linoleic acid, because of its bulky structure due to the presence of double bonds, it does not penetrate the fiber, consequently resulting in no favorable impact on protein loss.

(Summary can be found here...)

Mineral oil was found to not penetrate the hair strand in quite a few studies. Having said that, we don't need an oil to penetrate our hair strand to be awesome. A coating of oil - or silicone, or other hydrophobic thing - can reduce water retention and friction.

Related posts:
Weekend Wonderings: Oils good for our hair?
Coconut oil in hair products (with leave in conditioner recipe)
Conditioners: Adding oils - coconut oil (with various recipes)
Coconut oil? Coconut oil! 
Question: What oils are good for your hair?

If you want something to penetrate your hair strand, oils aren't necessarily the right ingredient, especially if you want moisturizing. (Coconut oil, yes. Unconfirmed for the rest.) You'd want to turn to ingredients like hydrolyzed proteins - silk or wheat to penetrate the hair shaft, oat to coat it - or humectants. If you want to coat your hair strand, any oil or butter you might like to use will work, as will silicones and some esters.

As an aside, there is a difference between moisturizing and hydrating. Moisturizing is about preventing water loss, which means you want to use emollients, like oils, butters, silicones, and esters. Hydrating is about maintaining an adequate level of water in our skin and hair, so you want to use humectants. Conditioning is about preventing friction damage, so you want to use conditioners for that. 

To summarize...
  • Hygral fatigue isn't a cosmetic chemistry thing - I've only seen it the once in that oft quoted study.  
  • Coconut, mineral, and avocado oils aren't polar.
  • Coconut oil can penetrate your hair strand, but mineral oil can't. I haven't found anything confirming that avocado or olive oil can penetrate your hair strand, although it seems like the monounsaturated fatty acids, like oleic acid, might. 
  • Every oil will form a coating on your hair, which will keep water out. 
  • Water penetrating your hair strand isn't always a bad thing, depending upon hair type. 
I'm writing this post because I want to create discussion - respectful discussion. There's something about discussions about hair and hair care that seems to bring out the worst in us, and it's not necessary.  If you wish to comment, please post your name somewhere in the post and be civil. I will delete any anonymous posts. (Sign off with a "Bye, (name)" if you don't have a Google account.) If we want to share information and learn, the best way to do that is to be civil because the moment someone is called "ignorant", they stop listening. If you would be embarassed to see a teenager you care about writing what you've just written, you haven't been civil. If you have links on this topic, please share.

I found a great trove of information at Ktani's Hair Sense on the topic. I really recommend you wander over there and take a look! And check out this post she wrote on Hair Protein Loss and Coconut Oil, Hygral Fatigue and Mineral Oil. Bookmark this page! I love her use of references in her posts and her willingness to question everything! Awesome awesome blog. (Why don't I have this on my blog roll? Well, I do now!)

I need to point out that I am no expert on African hair - everything I know I have learned from my textbooks - so I do not write this to act as if I am. (Although this topic of hygral fatigue isn't just about African hair types, most of the resources I found were for this hair type.) I know there are issues with breakage for the African hair type - click here for a very interesting read - and I, unfortunately, don't have any solutions. I'm also not an expert on curly hair, another hair type that I've seen associated with hygral fatigue. I write this post because it was interesting to me!

And thanks to the people who shared their thoughts and resources with me. I'm always about the learning, and I've learned a lot the last few days. As you can see, I'm still waiting for more information to come in! 

Related posts:
The chemistry of our hair: Overview
The chemistry of our hair: Medulla and cortex
The chemistry of our hair: Cuticle
Definition of good condition
Quick summary about damage
African hair types
Some interesting things I found about African hair types
Chemistry of our hair: Straight, curly, and frizzy hair! 


Maia said...

Super interesting as always. I'm a curly girl and African American. You hear so much about why you should or shouldn't do this or that with oils, so I appreciate reading the science behind it.

Judy said...

"Coconut Oil, Avocado Oil, Olive oil penetrate the hair shaft to make it stronger (J. Cosmet.Sci 52, 169-184, 2001) The study showed straight chain glycerides like coconut oil, avocado oil, olive oil easily penetrate into the hair."


Susan Barclay-Nichols said...

Great link! Unfortunately that blog doesn't link to the study, but I just found it and a few others! I'm at school at the moment, but I'll be reading these later tonight. Fascinating stuff! Thanks for sharing!

p said...
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p said...

Hi Susan, Terrific post! Oils and silicones both coat the hair, keeping water out. You mention that silicones keep water in, which is why they offer heat protection. Do oils keep water in and offer heat protection as well? Thanks!

Anonymous said...

Wholly unrelated, just heard we have an office closed because of flooding up your way and if I remember correctly your city is near a big river, long story short, hope you are and stay well (and dry).

Will Streeter/Cleveland, OH

Sally said...

I read that rinsing chia seeds and catching the water will create a protein rich rinse for your hair. Kind of a little different topic, but was curious if you had any comment or knowledge on it, and if it really provides a benefit. There's so much false information these days that it is so hard to know.

Thanks, Sally

Susan Barclay-Nichols said...

Hi Judy! I have written an entire post about the studies, which you can find here, and I've amended the post. What's interesting is that the study you note is quoted by so many blogs - seemingly hundreds of them - but none of them seem to have actually read it! It seems they are referencing the study through a Beauty Brains blog post that admitted later they got the reference wrong. The original study only looked at coconut oil and mineral oil, not the other oils noted, although there are other studies suggesting that oleic acid might be able to penetrate the hair strand. (Look at the linked post for those studies). Thanks for the information! And thanks for the great way in which you presented it to me. I was really wrong!

Hi p. As far as I can tell, anything that coats the hair shaft should be able to keep water in. (Again, look at the studies I quote above.) I don't know about heat protection, and I would hate to be wrong about that because you could end up frying your hair!

Hi Will. The flooding is in Alberta, near Calgary, about 10 hours' drive away from my house in the Fraser Valley. We do have a large river near us - the Fraser - but it's fine as of today! Thanks for worrying about me, though!

Hi Sally. I have no idea. Sorry. Our hair has a protein called 18-MEA, but I don't know if chia has it or if it can do anything for your hair if it does. I'm afraid I don't know much about those kinds of home remedies for hair, like using flax seed.

p said...

Thanks for the response, Susan! Could you do a post on the heat protection and silicones? I'd love to know more about the mechanism of action.

It's interesting to me that when you go to the salon, they wash your hair, apply a heat protecting product to your wet hair, and then blow dry. I would guess that the silicones in the heat protecting product would trap water... that water would get hot during blow drying, and some of it would vaporize, which would cause hair damage... but apparently that's not what's happening! I'd love to get a clearer picture of what's going on.

Sorry if you've already posted about this and I missed it!

Michele Clarke said...

I am even more confused on what my hair wants. The curls are very tight now but as the day goes on it gets fuller and fuller. I don't like that look. I like my curls being weighed down and almost flat against my head.

I use to have that look but the products I used then have newer formulas. hmm

Time to experiment.

Fire Fox said...

Superb series of articles here, much better than Ktani who mixes quality references with highly dubious ones and anecdotes, all referenced with equal merit.

"Tonya McKay holds a B.S. in Chemistry and an M.S. in Polymer Science. She was privileged to do her graduate research under the tutelage of Dr. Robert Y. Lochhead, a colloid and polymer physical chemist, world-renowned for his expertise and inventions in a variety of industries and applications, most especially cosmetics and personal care.

Upon completion of her master's, she spent several years working in industry as a research scientist, honing her skills and understanding in both the fundamentals of polymer science and applications thereof. Although her employment has not always been in the field of personal care and cosmetics during her career, McKay has worked on and led various research projects for major corporations in the field, both suppliers and end product manufacturers."

John Terry said...
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Michelle said...

Hello Susan, Hoping you see this comment in this older article. Wondering if you have any new info on Kukui Nut Oil with regard to hair care. I absolutely LOVE this oil but good info on it seems to be rare. I want to mix it with Fract. Coconut Oil and perhaps some Argan oil. This would be for a leave in style/conditioner. When I use Kukui nut oil, my hair instantly calms (defrizzes) and is so shiny. Kukui nut oil does this better than anything else I have used. Hoping there are other discovered benefits as well. Thank you for the articles you do provide, just hoping there might be more by now. It is such a great oil!

Susan Barclay-Nichols said...

Hi Michelle! I haven't found anything more on kukui nut oil and hair. If you like it, then use it! It's one of my favourite oils, too!