What is the scientific basis for the advice to avoid sulfates?

PerryPerry Administrator, Professional Chemist
I follow this one page on Reddit about /hairscience.  In truth, it's filled with anecdotes much more than science but it is a good way to keep an eye on what is going on with consumers / cosmetologists in terms of beliefs in the marketplace.  On this site there is the strong belief that sulfates are bad for hair. So, I posted a question there to see if there was any scientific support for the idea. You can read it here. 

But I thought I'd post the question here.  Is there any scientific studies of which you are aware that convince you sulfate-free shampoos are better to use than sulfated ones?


  • PharmaPharma Member, Pharmacist
    edited June 2019
    First, I don't have an answer to your question (I didn't search thoroughly for it).
    Second, I'm good with educated guesses and applying/extrapolating from theory to practice.
    I can't see anything that could possibly explain the "sulphates are bad" attitude except that sodium dodecyl sulfate is fairly aggressive aka efficient (not just for hair but also to skin, dishes, and so on). Sodium laureth sulfate is milder but hey, it's still a sulphate and it still kills cells in a petri dish better/faster than lets say non-ionic surfactants. Sulphates are, like PEGs, not super well degraded, contribute to eutrophy, and because the other bad guys like petroleum and parabens are getting an old hat, we need a new bad guy and another reason why.
    It's a freaking witch hunt out there! If warts on noses don't cut anymore, let's burn ginger gals!!!
    Something that got me smiling: Some company (was it Evonik or Cosphatec?) calls the "new good guys from the white-list" simply "label friendly", not green chemistry based, eco-friendly, from renewable resources, CO2 neutral, sustainable, vegan, and fairtrade ingredients. Simply "label friendly" :smiley: .

    PS Pssst, don't tell them that there's only a minor difference between sulphates and sulphonates ;) .
  • So much nonsense.. I couldn’t help it and commented on a couple of posts but then realized it’s useless. They say SLS is used in clinical studies as a skin irritant... yes, undiluted, covered and left for hours! If you drink too much water too fast you will die too. Doesn’t make water a poison.
  • Having said that, I personally don’t like sulfates on my chemically treated (or should I say chemically abused) hair. I use SLES/CAPB shampoo once in two weeks because I love silicones and polyquads that tend to build up. 

    Everyone can have their preferences. But the fact you don’t like the taste of broccoli doesn’t justify starting a fear mongering campaign and say broccoli cause cancer.
  • PerryPerry Administrator, Professional Chemist
    @ngarayeva001 - That sub is extremely frustrating at times. It is decidedly not scientific despite the name. However, I do find it helpful to keep an eye on what some consumers believe and even more interesting to understand why they believe it.

    Of course, I'm similarly interested in what people believe on our forum and why. It's just that here people don't take as much offense when asking them to clarify what they meant or support their claims.
  • JonahRayJonahRay Member
    edited June 2019
    I'm not sure there really is a strong scientific basis to it. I notice with skincare especially, on the internet people tend to share their 'knowledge' like it's straight up fact...."Silicones will clog your pores and give you acne" for instance - and they won't even allow much discussion on it. "Sulfates are bad!" no questions asked. I find a lot of consumers don't know something is bad until they are told, granted many don't have scientific background and can't make truly informed choices. Brands that label sulfate free have given the consumers information that they expect comes from experts that they can trust and therefore believe sulfates to be bad.

    When I was looking for the perfect skin cleanser for myself - I read a few journal articles comparing different surfactants and found that SLS interacts with the lipids in the skin more than lets say sodium cocoyl isethionate. It's possible this type of information kind of just spreads throughout each category - if it's more disruptive to skin, it must be more disruptive to hair. You see this with trending ingredients - clay masks for both the skin and scalp, charcoal face masks, hair masks and toothpaste.

    Additionally suppliers of raw materials tend to push these ideas to manufacturers pretty intensely which I think trickles down into the marketing of the product and consequently down to the consumer.

    Jonah Ray | Owner & Founder

    build (skincare) | buildskincare.ca

  • PerryPerry Administrator, Professional Chemist
    @JonahRay - yes, suppliers also push these kinds of misconceptions. They are motivated to upsell more expensive surfactants.

  • GuntherGunther Member
    edited June 2019
    It only proves that the word Science draws crowds
    Even if there's no science in /r/HaircareScience, just anecdotal experiences.

    By the way, they should have called it /r/CurlyGirlShills instead.
  • PerryPerry Administrator, Professional Chemist
    @Gunther - they also love Olaplex

  • ozgirlozgirl Member, PCF student
    There is a statement in the discussion section of the CIR report for SLS that mentions the potential for damage to the "hair follicle" due to deposition of  SLS. I am wondering if this has been misquoted somewhere along the way and changed from 'hair follicle' to 'hair' and then repeated until it was just accepted as "fact".

  • Lady_BLady_B Member
    edited July 2019
    Well, there are some studies available too that link SLS with more irritation. I thought it was you who mentioned on Beauty Brains that SLS has a smaller molecule size and might more readily penetrate and therefore stay deposed in hair follicles, no?

    Here is a good comparison table: https://www.sciencedirect.com/science/article/pii/S0278691506003140

    Sodium Lauryl Sulfate


    Ammonium Lauryl Sulfate


    Sodium Laureth Sulfate


    Sodium Lauroamphoacetate


    Sodium Myreth Sulfate


    Sodium Cocoamphoacetate


    Cocamidopropyl Betaine


    Coco Glucoside


    Disodium Cocoyl Glutamate


    Disodium Laureth Sulfosuccinate


    Decyl Glucoside


    Lauryl Glucoside


    Disodium Cocoamphodiacetate




    Laurdimonium Hydroxypropyl Hydrolyzed Wheat Protein


    Sodium Cocoyl Hydrolyzed Wheat Protein


    Sodium Cocoyl Hydrolyzed Wheat Protein Glutamate


    Laureth-7 Citrate


  • Lady_BLady_B Member
    And this is directly from the manufacturer:

  • Unfortunately all these test show different results. Zein protein chart is different from HET-CAM chart and I don’t know which one is more accurate.
  • Lady_BLady_B Member
    I think they just paint different parts of the picture and we need to take all of them into account. However, as Perry mentioned, if someone doesn't have an issue with SLS, why bother looking elsewhere? If the surfactant is "too effective" wouldn't it be easier and more economical just to water it down?
    I use Perry's shampoo (it is my "gold standard" whenever I play with my own shampoos), and skin irritation is minimal, although it uses SLS and is pretty concentrated (I always forget to use less than other shampoos and end up with a ton of foam). 
  • In my 26 years as a hairdresser and an educator for professional colorists, I can tell you with certainty that the majority of stylists believe marketing is science. I think it was Pureology (around 15-20 years ago) that first came out with a marketing story linking sulfates to color fading that really took off. If an educator comes into your salon and says sulfates make color fade, then that’s science based facts?. And their brand took off so quickly that there were soon many others. Once a trend like that hits the mass retailers and clients are seeing the same marketing claim everywhere, everyone in the hair world seems to just accept it and the word spreads like gospel. So I don’t think there was much science anywhere, just testing done by biased manufacturers to support claims. 
  • PerryPerry Administrator, Professional Chemist
    @Lady_B - indeed SLS can be shown to be more irritating. However, the claims that people make to "avoid sulfates" is not focused on irritation. They specifically say that it is bad for hair. 

    Thanks for the article link.  For anyone who is curious, here is the full paper.

  • chemicalmattchemicalmatt Member, Professional Chemist
    To answer Perry's original question: I know of no such research paper determining SLS as a harmful element to humans. As for the well-known irritation potential: that is so easy to formulate out of your shampoo product! Once you add counter-irritants (ISML, amphoterics, etc.) that index number comes way down. Regarding @colorfuljulie narrative - she is right. Pureology and other pro brands made claim that SLS was fading color too fast from dyed hair, and they were right. It works too well as a surfactant! That is where I remember the entire "sulfate-free" trend starting more than 20 years ago: in the pro salon and with dyed-hair customers. It escalated from there to the point where too many Chemists Corner followers believe SLS is wrong to use for the wrong reason.
  • Our oceans are dying, sea water is too acidic.

    We know that everything we use in our homes and factories go down the drain, and guess where that ends up?

    I believe that the oceans give us life. We need nature, nature does not need us :)

    "SLS is not expected to bioaccumulate or persist in the environment, which is a good thing, but it is known to be toxic to aquatic organisms as noted in the International Chemical Safety Card (ICSC) Database. So, considering it's getting rinsed down our drains from several personal care and cleaning products we use every day all over the world, this is something to consider."

    Love and light  <3
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