Sodium Laureth Sulfate

sodium-laureth-sulfate

Sodium laureth sulfate is in just about every shampoo and foam bath, as avid readers of ingredient lists can confirm.  The name tells you pretty much what it is, if you know about these things.  It is the sodium salt of sulfated lauryl alcohol, which has been ethoxylated.  If you had hadn’t ethoxylated it, it would be sodium lauryl sulfate.  If you hadn’t added the sulfate group it would have been sodium laurate.  And sodium laurate is a form of soap.  So in a sense it is souped up soap.  Soap that has an increased ability to foam at the cost of reducing its ability to cleanse.

It is possible to derive the starting material, the lauryl alcohol, from petrochemicals or from animal fat, and both of these have been used in the past.  But the overwhelming majority today comes from vegetable oils.  You get a better foam if you use lauryl alcohol sourced from vegetable sources, of which the main ones are coconut oil and palm oil.  Typically the choice of source is determined by price and availability and it is quite feasible to use a blend of both as a starting point.  You can choose to use just coconut oil and call the resulting chemical sodium coco sulfate.  You’d need to work pretty hard to distinguish sodium lauryl and sodium coco sulfate in the lab.  You’d certainly not see any difference in their behaviour.

The ‘eth’ bit laureth comes from the fact that the lauryl alcohol has been extended by adding ether groups to it.  These make the lauryl alcohol a little bit more soluble in water and a bit more bubbly. They are the reason you get a richer foam from a shampoo than you get from a soap, and you get it much more easily.  In fact what we call sodium laureth sulfate is actually a mixture of molecules that have different amounts of ether, and some have none at all.  So all sodium laureth sulfate contains some sodium lauryl sulfate as well.

Both these materials are present in the vast majority of hair shampoos and foam baths that you can buy on the market at the moment. In fact, in 2000 when some German researchers wanted to investigate this material they found that 97% of their prospective subjects already had it on their skin.

The reason it is popular is that it is pretty much the ideal material to create bubbles. There is a lot of money in bubbles. People will almost always pick a product that gives a “rich creamy lather” as my marketing colleagues would call it. I once gave a talk about shampoos to an audience of chemists and blew a large bubble to demonstrate how good at forming bubbles sodium laureth sulfate was.  It got a round of applause.  Everyone loves bubbles.

It has also been known for a long time that sodium lauryl sulfate irritates the skin. This is so well known that when skin irritancy is being studied sodium lauryl sulfate is the generally agreed test material used to do it. A lot of the skill of formulating shampoos and cleansers involves coming up with ways of maximising the bubbles while minimising the irritation.  This can be done pretty well in fact.  Despite its intrinsic irritancy, most people will find that for them the shampoos formulated with sulfates will be a lot milder than sulfate free ones.

So most people will find that sodium laureth sulfate is a material that they will have no problem with.  If you have particularly sensitive skin you’ll probably find that you experience less short term irritation with standard formulations.

But there may well be a more subtle long term problem.

It has recently started to become clear why sodium lauryl sulfate has this harmful effect. If you consider the structure of the skin, the outer layer is the stratum corneum. This is made up of dead cells that mover up from the basal layer becoming flatter and harder as they go. These cells are held together by small links, called desmosomes. These are made of protein and the rate at which these links break controls the rate at which the dead cells on the surface of the skin are sloughed off. This is controlled by an enzyme called stratum corneum chymotrypsin enzyme (SCCE) – which is the body’s natural exfoliating agent. It turns out that sodium lauryl sulfate interferes with this process altering the skins ability to lose dead cells.

So what do we make of all this?  It turns out that sodium lauryl sulfate might have an adverse effect on your scalp, but the skill of formulation chemists prevents this from being particularly noticeable.

It is hard to say if this matters or not.  Certainly most people use shampoo containing sodium laureth sulphate regularly.  Many people use it daily.  There doesn’t seem to be any obvious harmful effects even after decades of use.  But maybe our scalps are just a touch drier than they would be if we used less?  If anyone has studied this in detail I haven’t seen the research.  What would be most interesting would be to follow a group of people who have given up using shampoo and see what happens to the state of their scalps.

I am unimpressed by the claims made for sulfate free products.  All detergents have similar structures and there is simply no evidence that it is the sulphate bit of sodium laureth sulfate that is what makes it irritating.  In fact if I had to guess I’d focus on the sodium part.  There is some evidence that replacing sodium with alternatives like triethanolamine makes shampoo formulations milder.  The sulfate free idea seems to me to be simply a marketing ploy.

Skin irritancy is not as well understood as we would like.  I’d love to know the answer, but all I can do is scratch my head.  In fact we might all be scratching our heads a little more often than we need to.

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26 Responses to Sodium Laureth Sulfate

  1. Maire Gaffney says:

    It’s interesting to hear some research is going on on SLS. Is there any real alternative? On a completely non-scientific personal basis it seems to me that my scalp and face has become increasingly irritated over the years (difficult to wash hair without getting shampoo on the face) and intolerant of any kind of shampoo. Hair products have become so sophisticated it is easy to look like a bag lady in comparison if you don’t use them.

  2. Annette says:

    Hi Colin,
    I’m a little confused here. You seem to be using the terms : sodium lauryl sulfate (SLS)and sodium laureth sulfate (SLES) interchangeably. It is my understanding that they are two different chemicals, with SLES being a milder form (?) of SLS…

  3. sian hendra says:

    YES there are alternatives! Try the range I sell…www.uk.yrorganic.com/shop/sianhendra for completely artificial ingredient-free skincare products. Neals Yard Remedies only use natural and organic ingredients. Why use anything else if it’s unnecessary? Natural ingredients = natural skin. Take a look at my website for more information.

  4. Colin says:

    @Maire I hesitate to offer alternatives when I am not sure that there is any really good data comparing different ingredients, but the other sulphates like ammonium and triethanolamine might well be milder in the long run.

    @Annette Sodium laureth sulfate (SLES) and sodium lauryl sulfate (SLS) are very similar, but SLES is a bigger molecule than SLS, This means that for the same weight you have fewer molecules. For that reason alone SLES is going to be a bit less irritating. Whether SLES is an intrinsically less irritating material I don’t think anybody knows, and if it were the difference might be too small to make any practical difference.

    @sian – I hate to be the bearer of bad news, but Neals Yard shampoos do effectively contain sodium lauryl sulfate even if it isn’t on the ingredient list. They contain ammonium lauryl sulphate but also disodium coco-glucoside. In solution both these materials split into two, so you have ammonium and sodium in solution. In effect you end up with the same product as if you had used sodium lauryl sulfate and ammonium coco-glucoside.

  5. Dene Godfrey says:

    @ Sian – natural doesn’t mean safe any more than synthetic means dangerous. Some in the cosmetics industry would have you believe this, but there is neither science nor logic behind this belief. Perhaps you might like to read this article, which explains this in more detail. http://personalcaretruth.com/2010/05/natural-is-safe-and-synthetic-is-dangerous-truth-is-safe-and-myths-are-dangerous/

    And I hate to tell you this, but Neal’s Yard use some petrochemically-derived ingredients in many of their products. They are substances that do exist in nature, but they are synthesised from petrochemical feedstock as it is not commercially viable to extract them from nature. For my money, they are, therefore, petrochemicals!

  6. Dene Godfrey says:

    @Sian – I’ve also taken a quick look at some NYR ingredient listings:

    This is the Revitalising Orange Flower Shampoo:

    Aqua, Ammonium lauryl sulfate, Disodium coco-glucoside citrate, Alcohol denat.*, Hydroxypropyltrimonium honey, Cocamidopropyl betaine, Calendula officinalis (Marigold) flower extract*, Symphytum officinale (Comfrey) leaf extract*, Arctium lappa (Burdock) extract*, Citrus aurantium amara (Orange flower / Neroli) flower extract*, Simmondsia chinensis (Jojoba) seed oil*, Camellia kissi (Camelia) seed oil, Citrus aurantium amara (Orange flower / Neroli) flower oil, Rosmarinus officinalis (Rosemary) oil*, Sapin grandis (Grand fir) oil*, Passiflora edulis (Passion flower) seed oil, Oryza sativa (Rice) bran oil, Euterpe oleracea (Acai palm) fruit oil, Moringa pterygosperma (Moringa) extract, Cyclodextrin, Dextrin, Guar hydroxypropyltrimonium chloride, Levulinic acid, Glycerin, Potassium sorbate, Sodium sunflower amphoacetate, Citral, Citronellol, Farnesol, Geraniol, Limonene, Linalool.

    At least 6 of these ingredients don’t exist in nature and are, therefore, artificial. They may have fairly “natural-sounding” names, but they are NOT natural. They may be DERIVED from nature, but if you react two substances together to form a third, the third substance is synthetic, irrespective of the origin of the starting materials. You should not be claiming the products to be 100% natural, because this is not the case. Either way, they are no more safe or dangerous than most other products on the market (I refer you back to the article I linked in my previous comment).

  7. Dene Godfrey says:

    @Sian – an acknowledgement that you have actually read the comments would be appreciated, even if you don’t fully understand the implications for the claims you’ve made.

  8. Charlie says:

    Hi Colin – thanks for this informative article, it’s nice to read such a balanced view!

    I’ve been looking into SLS / SLES and once you get past the hysteria, it seems that most credible sources reluctantly agree that they’re kind of a necessary evil – they won’t do you any good, but they won’t kill you.

    My question is regarding the penetration enhancing abilities of SLS – reading this page:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3283952/ makes it sound as if SLS will pretty much melt our skin and compromise the deeper layers. (Is this considered a good quality by cosmetologists? Like, if you use a face wash with SLS it will get further into the skin with the rosehip oil also present on the ingredients list?) I don’t have a background in chemistry, so I don’t really know how to “read” these results and I’d appreciate your thoughts. Sorry for the long post!

  9. Colin says:

    Thanks for the question Charlie. That reference is a review paper, which is a good place to start. I have to say it doesn’t read as if the author has done much work himself – it looks a lot more like he was about to start working on skin penetration and decided to try and get a paper out of all his preliminary research.

    I think he is a bit too optimistic. Working on skin penetration soon makes you realise what an effective barrier the skin is.

    Surfactants like SLS do disrupt the skin’s barrier function, which can lead to an increase in permeability to drugs and toxins. It is pretty hard to do enough damage to increase it very much though. If you could, it would be quite handy because you could deliver drugs like insulin via patches rather than injection. Specifically, rosehip oil is a good source of antioxidants and some retinol like substances. But I doubt applying it with SLS will lead to a significant increase in the amount that gets through.

  10. Charlie says:

    Thanks for that. Also, when you say that SLS interferes with the process of the skin losing dead cells, does that mean we lose more cells, or that we don’t lose enough (possibly requiring exfoliation afterwards)?

  11. Colin says:

    Curious you are.

    It means they are released in large clumps rather than as individual cells. A single skin cell is too small to see and rapidly disappears. The clumps hang around longer. They can give the skin a dull look, or even a powdery appearance. If you wash your hands a lot over a few days you can find your skin begins to look like it has a fine white powder on it.

  12. Charlie says:

    Thank you! I am curious indeed :-) It’s so good to find a reliable source of info because random googling about anything SLS-related brings up a ton of rubbish!

  13. Sara a. says:

    Hi, Colin
    Thank u for the article
    I have a question: do u know if sodium coco-sulfate is worse, better or the same as SLS and SLES?
    Thank u :-)

  14. Colin says:

    Good question Sara. In fact in the first draft of this post I talked about that, but I cut it because it confused the issue. Sodium coco sulfate is virtually identical to sodium lauryl sulfate. It is made from fatty alcohols derived specifically from coconut oil and tends to have a bigger range of carbon chain lengths than SLS, even if the average chain length is the same. You’d only be able to tell the difference with some pretty sophisticated chemical equipment. Companies that use it and then claim SLS free are being pretty cynical.

  15. Seppo says:

    Truth to be told, sometimes I wish I could shoot all the marketing people selling cosmetics and personal care products.

    My anecdotal evidence suggests that SLS in shampoos irritates my skin and causes painful cystic acne on my scalp. Of course this is purely anecdotal observation and I could be wrong about it, but I’ve seen big improvements from switching to ‘SLS free’ shampoo.

    My desire to shoot the marketers stems from the near impossibility for a layperson to make sense of this and find alternatives. As you mentioned, the product can have SLS-like effect even if it doesn’t have SLS. And we all know where we can stuff all the ’100% natural’ claims…

    My apologies for the tone, but this is a really frustrating issue.

  16. Colin says:

    I know what you mean Seppo. You’d have thought that straight forward information was the best way to sell things. With regard to your problem, I find that when I am testing surfactant rich shampoo formulations and use them more often than usual I get dry skin, and sometimes it even breaks out into small patches of bleeding. Rather than try and find the ideal chemical combination for you maybe try looking at frequency of washing and how much you use. You might find that you can get away without shampoo at all say every third wash. Just a thought.

  17. Dene Godfrey says:

    I’ve just seen information on a UK cosmetic manufacturer’s web site claiming that they only use “natural sodium lauryl ether sulphate”. Wow! :-/

  18. Colin says:

    Natural sodium lauryl ether sulfate? Is it dew picked and collected in wicker baskets?

  19. Amy says:

    Thanks for this informative post. I actually prefer using shampoos containing SLES/SLS as I find that my hair and scalp feel cleaner after using them. I once switched to a sulphate free shampoo and really hated it as it didn’t foam and I felt like I had to use a lot of the product to be able to spread the product round and get the clean feeling that I desired. On top of that my scalp didn’t feel clean and felt itchy/still greasy afterwards afterwards!

    To be fair though I don’t wash my hair everyday, just two to three times a week with dry shampooing in between. I would imagine that if you were to wash your hair more frequently you would feel the dryness that you talk about. I use a clarifying shampoo once a week, whish is drying but follow with a moisturing conditioner afterwards.

  20. Hello Colin!
    I have just stumbled across your Blog as I am doing some reading and preparation for my upcoming trip to the Sustainable Cosmetics Summit in New York next week.

    To briefly brooch the subject, sulfate-free shampoos and conditioners have gained popularity as it has been observed that sulfates strip colored hair proteins of the deposited dye, as well as affect chemically-treated hair from retaining the treatment.

  21. x says:

    Hello,

    Thank you for the article. It is interesting to learn that sulfates are almost unavoidable, as I myself have been trying to avoid them. My sister suffers from eczema on her hands which is exacerbated when she uses drugstore shampoo (with SLS/SLES), but seems to get better when she switches to a natural “SLS-free” shampoo. I’m starting to think that perhaps there are other ingredients in the drugstore shampoo which could be at least partly responsible for the irritation…

    Can you address the risk of 1-4 dioxane contamination in SLS/SLES as a result of ethoxylation? I’ve heard much about it, but am not sure what is true/what isn’t true.

    Thank you!

  22. Frances says:

    Could SLS be responsible for the BCC (basal cell carcinoma) that I got on my scalp I have always hated sitting in the sun and never go out in it if I can help it. Also my friend said that you also get SLS in toothpaste and was told that it could give you ulcers in the mouth if you were susceptible to them (I now use sensodyne that does not have it in)

  23. Colin says:

    Hello Frances. I can’t think of any reason SLS could have contributed to BCC on the scalp. I suppose it is just conceivable that it dried the skin and so reduced the effectiveness of the skin’s protective mechanisms. But that would be the case for any surfactant and any shampoo formulation. As to mouth ulcers, again I doubt it and I can’t think of any evidence to suggest it is a problem. But it isn’t totally inconceivable until someone does a proper study.

  24. iMarie says:

    I am also curious about sulfates contaminated with 1,4-dioxane. Is it a significant risk?

  25. Millie says:

    I think I am allergic to SLS however it is hard to tell. Every shampoo I have used with out SLS has worked well for me. When I do use shampoos with SLS I get a very itchy and flaky scalp which is very unattractive, but who knows it could be some other ingredient, but I am currently using Pureology and I LOVE IT!

  26. Vicki says:

    Hi, I’m new to this discussion and see i have stepped into a minefield. I have seen SLS in bar soaps too, I thought you could get a bubbly lather with certain oils so why use SLS? And why would bar soaps contain parabens when they last for at least 36 months. So when i make soaps and am tempted to say SLS and paraben free, is it a pointless exercise?

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