Saturday, June 23, 2012

Question: Is there any science to using a vinegar rinse on your hair?

Anonymous asks in this post: I was wondering if there might be any science to back up using a vinegar rinse? I agree that using baking soda to wash hair is a terrible idea, but I have found a vinegar rinse (after shampooing, before conditioning) invaluable. My hair is much smoother and more manageable. I have heard the acidity closes the cuticle, but am yet to see the scientific backup to this. One odd thing I found - I once accidentally did the vinegar rinse between the 1st and 2nd shampooing, and it made the 2nd shampooing impossible. I can't remember exactly how, just that the shampoo wouldn't 'go' through my hair somehow, and I wondered if the shampoo couldn't open up the cuticle after the rinse. My question is, is this, or some other reason, at least theoretically possible? I use cheap white vinegar because I think using apple cider vinegar would be a waste of money, about 1 part vinegar to 10 parts water. I have also used very dilute citric acid and found the same positive effects.

There's a lot of talk about "sealing" our cuticle, but there's really no such thing. Our cuticle is made up of scales that overlap like roof shingle - it isn't one big thing that needs to be sealed, but a bunch of things that need to lie flat-ish.  (Click here for more information on the cuticle! And look at the picture above.) We want our cuticle scales to lie as flat as they can so they won't be torn off or won't allow stuff to pass into our hair shaft. We do that by using things like conditioner that are positively charged and will adsorb to the hair strand to create lubricity and reduce friction. (Click here for information on what damage means to our hair and how it happens.)

As an aside, cationic polymers like polyquat 7, polyquat 44, or honeyquat - amongst others - improve the adhesion of our cuticles to the hair shaft, which makes them harder to remove when we damage them through friction, like when we comb our hair or get it caught in the door of a car! Cetrimonium bromide is also awesome for this! (Reference: Handbook of Cosmetic Science & Technology, 3rd edition). 

I've looked through my various textbooks and did quite a few searches, and the only thing I could find was from page 526 of the Handbook of Cosmetic Science & Technology,  third edition, which noted it is suggested to use a vinegar rinse after bleaching to stop the oxidative damage to our hair. They suggest "an acidic bath" using "lemon juice or citric acid or diluted vinegar" followed by a deep conditioner. I could find nothing science-y to suggest that it is necessary for normal hair that hasn't just been bleached.

Having said that, I think there are a lot of people who swear by vinegar rinses. One of the main reasons we use conditioners is to increase lubricity, which reduces friction and combing forces, and I'm not sure that vinegar offers that quality, so I am a little worried about its long term use in place of conditioner. Once your hair is damaged, you can't undamage it. You can only mitigate the damage for a while.

I don't get the appeal of the vinegar rinse. I've tried it a few times, and my hair feels really awful afterwards, as if I hadn't conditioned my hair. My opinion isn't really relevant to this discussion, but I thought I'd let you know that I have personal experience with using vinegar! 

I agree with using white vinegar rather than some fancier version. If the goal is to use something acidic, it doesn't matter what type of vinegar you use - if it's registered as lower than 6 on the pH scale, it'll work just fine. If you want it to be a tasty treat on fish & chips, then you might enjoy a malt or apple cider vinegar!

I think what you found with the shampoo was an inability to lather and foam. I'm not really sure how that happened. I think it's like when you drop soap into a bathtub of bubbles - you add something to the mix that reduces foam, lather, and bubbling.

So what's the verdict? I don't really know. I couldn't find anything science-y to confirm that vinegar rinses on normal hair is effective or desirable, but I didn't find anything to say we shouldn't do it*, so if you like it and want to use it, then have at it! Just be careful you aren't damaging your hair permanently.

*Footnote: I also didn't find anything to say we shouldn't use apple sauce, grass clippings, or milk after shampooing, so my inability to find information decrying using vinegar doesn't constitute an endorsement of using it as a rinsing agent. 

Thanks for the great question, Anonymous! And if you have any science-y type information on vinegar rinses, please send them along to me as I would love to learn more about this concept!


Sciarretta Farms said...

It may have something to do with whether you have hard or soft water - it didn't work for me with soft water, but it sure made a difference where I live now with hard water.

I have a lot of deposits in the water and we wash faucets etc with vinegar as the only way of getting deposits off. So I am wondering if the reason it helps is because you get deposits on your hair as well?

Carol said...

I don't have any studies to back up my statement, but I would say that the vinegar cuts the lather. When I wash my cloth diapers, I use vinegar in the rinse to "clean out" the soap residue.

I like using a vinegar rinse, it makes my hair more manageable. I use it after I've rinsed the shampoo out and before my conditioner. So I will rinse it out. It is only my observation of my routine that I let you know. I have deliberately left out the vinegar rinse a few times and I really didn't like the results. I used the same shampoo and conditioner, so the only conclusion was that my hair likes the addition of a vinegar rinse. I know it doesn't work with everyone and I would never think of replacing my conditioner with just the vinegar rinse.

Jessica said...

I sometimes use vinegar rinses after conditioning (definitely agree you should NOT replace conditioning with vinegar rinses, for all the reasons Susan stated!) I have highly porous hair (I think because of the shape of each strand - flat and spirally) and the acidic rinse seems to help with it. On a side note for anyone who wants to try them: if you use an acidic rinse and find that your hair feels icky afterward (like, rough or dry), consider trying again and upping the dilution factor. 1 cup water to 0.25 c. vinegar is an oft-quoted ratio. Of course, if you love to thrill the scientist in you, you can always make up several different ratios and test each's pH. You don't want something crazy-acidic...there is such a thing as too much of a good thing. :)

Danica said...

Great article Susan.
I'm in the anti vinegar boat. I don't really want my hair smelling like a salad even if it does dissipate. Ewww...The thought just makes me cringe. Can you tell I'm not a Vinegar fan even for food?
I also color my hair and I heard that vinegar can fade or alter your color- leaving you with a brassy mess. Not sure how true it is but it makes sense that it would.

I love my smelly shampoo and conditioners and my syndets I buy from a friend. :) I can't see altering these scents with vinegar.
Thanks for the article and the unbiased info as always.

Sara @Osmosis said...

I've not tried it on my hair, but have been using it instead of fabric softener in the washing machine. Since I switched to making my own laundry soap I noticed that hair in the wash would stick to the clothes. After adding the vinegar, the hair is no longer sticking to the clothes. We do have hard water, so maybe that's why it's helpful. I may give it a try as a rinse for my hair, but follow it with a conditioner.

Mychelle said...

I do this occasionally with ACV, mostly because I've done it since I was a kid. My mom would pour vinegar on our heads & we would complain! Nowadays I do it once every few weeks or so. Since moving to a mountain town on well water build-up has been an issue and the ACV really does seem to cut right through it. I always do the rinse after shampoo and before conditioner. It leaves my hair soft and shiny., and not smelling too vinegar-y.

mamirican said...

I use vinegar in the washer when I use too much detergent and get too many suds, the vinegar breaks down the suds and the clothes rinse out better. Maybe that's what happened to her shampoo after the vinegar rinse. Don't know how it happens, but it cuts through the suds.

catherine said...

I recommend a shower head filter for those with hard/well water. We have one...we change the filter maybe every 6 months.

Before the filter my whole family had dry tight skin and dry hair. We switched from suave/etc products to more expensive health food store 'natural' products and didn't notice a difference.

But once we got the filter everyone noticed an improvement. I use the shower filter for my son's baths too...takes longer to fill tub than regular tub faucet but it's totally worth it. And besides I haven't found a tub faucet filter.

Tara said...

Here is the Beauty Brains blog that posted on reasons why vinegar might be helpful depending on your water type:

It would seem there is a scientific reason to back up its use :-)

Christine E. said...

This was my question and I want to thank Susan for answering it, and everyone here for all this helpful additional information. I've only just had a chance to catch up on this blog, so I didn't see my questions was answered till now.

I think my water here is hard too, and this sounds like a very plausible explanation as to why the vinegar rinse helps. I had a book once that talked about vinegar hair rinses and hard water, but the book was also full of BS so I long ago dismissed anything I read in it. Basically it claimed in some mythical utopian hair era of the not-too-distant past, everyone washed their hair with castile soap and had perfect, shiny, manageable hair - and then of course the evil companies invented unnecessary garbage like shampoo and conditioner. Then it was suggested we can achieve the same hair perfection if we use castile soap BUT today's water is too hard so we must add a vinegar rinse. Seriously.

@Carol That's a good point, I too use vinegar to rinse my laundry. I have very sensitive skin and found the vinegar rinse stops my clothes from irritating me - I presumed because it gets out all the residue. But it didn't occur to me this might be why it cut the lather and slip of the shampoo - duh to me.

This is a great community here, it is really wonderful to read from like-minded people who are trying some hair and skin tips but not rigidly following the methods proposed by the true believers. The vinegar rinse fanatics swear you can use it in place of conditioner, which I quickly found was not true. But it was hard to ignore how much better it made my hair when I used it between shampooing and conditioning. And getting the same results with white vinegar or citric acid showed me it was likely the acidity, not anything special about ACV.

I think it's important to adapt to what you observe works, as well as try to understand the science behind why it works. I love hearing from other people that approach things the same way.

Thanks again, everyone. xo

Soes said...

On the other side: when people get a relaxer of a perm in their hair, the stuff they use is very alkaline one(around PH 13 I recall, just like oven cleaners and such), which supposedly opens the cuticle.
So I can imagine that something acidic would close it again.

Bailey said...

Hi Susan,

Just my 2¢ worth on the subject of using a dilute vinegar rinse on hair.

For years I had such a flaky scalp it came off in 'plates', I tried different shampoos & conditioners. Didn't matter if I used city water or rain water. Started using a dilute vinegar rinse after shampooing, then plain water rinse, then conditioner in the hair. Now, I no longer shed my scalp like a lizard! (My hair doesn't seem to mind either way, but my scalp certainly seems to benefit from it.)

I realize this is "anecdotal evidence" only. YMMV. ;)


Elena said...

Use of acetic acid on hair has nothing to do with chelation. It plays around the pI of keratin. Find a good "protein chemistry" textbook: it contains all the science you need.

Susan Barclay-Nichols said...

Sorry, Elana, but I don't know what the "pl" of keratin is. Could you share more? I've consulted many textbooks for this topic, as you can see from the post. Perhaps you could pass on the names of those you consulted to make my search easier?

Elena said...

You seem to have overlooked the chapter about Isoelectric point of proteins. All textbooks have it.

The pI for keratins varies between pH 4.4 and 8.3
What will happen to the negative electric charge of hair keratin when you rinse your hair with a liquid that has pH 3.5?
Yes, it will become positive.

So, vinegar (as any other acid) has a similar effect on hair as cationic surfactants, though the mechanism is different.