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Nitrosamines – Where they are and where they are not!

February 24, 2009

The internet is great. You can post what you like when you like and in no time at all you have created for yourself an urban myth. No need to worry that you are not a chemist or toxicologist or doctor or anything, post a good enough story and people will believe you!

Where they are not.

Well I am happy to be proved wrong but I can’t see ANYWHERE that Sodium Laureth Sulphate or Sodium Lauryl Sulphate are in any way shape or form Nitrosatable surfactants. I doubt that many will believe this because typing “nitrosamines” into google gives you over 327,000 hits.  In that mass of data are a frightening number of articles sighting SLES and SLS as dangerous due to their propensity to form nitrosamines.

As a chemist I have dug around on this one. How can SLS or SLES be Nitrosatable and create nitrosamines? They don’t even contain the element nitrogen in their structure – look for yourself on the wikipedia SLS entry.  Nitrogen is not even used in the manufacture of either products so it would even be hard for nitrosamines to be present as contaminants. Dioxane yes, nitrosamine NO.

Now, it is true that some surfactants are nitrosatable. A patent listed on Free Patents Online: Chemical compositions for inhibiting nitrosation reaction in toiletries and cosmetics outlines which surfactants could react to form nitrosamines. Here is an extract:

” Nitrosatable surfactants include anionic surfactants such as the triethanolamine salt of C12/C14 fatty alcohol sulphate, triethanolamine salt of lauryl ether sulphonate, triethanolamine/diethanolamine salt of dodecylbenzene sulphonate, triethanolamine/ diethanolamine salt of cetyl phosphate, triethanolamine salt of dioctylsulphosuccinate, sodium-N-lauroyl sarcosinate, sodium-N-methyl-N-alkyl taurate, and sodium-N-octadecyl succinamate; amphoteric surfactants such as cocoamphocarboxylglycinate and cocoamidopropylbetaine; nonionic surfactants such as tallow amine ethoxylate, lauryl dimethylamine oxide and other amine oxides and coconut fatty acid diethanolamide; and quaternary surfactants such as stearyl dimethyl benzyl ammonium chloride.”

What this says is that if you react something like Sodium laureth sulphate with Triethanolamine you get a triethanolamine salt. THAT can form nitrosamines because Triethanolamine  is an amine. Amines contain nitrogen. Nitrogen is needed to form nitrosamines! SLS and SLES do not contain nitroge. The above is talking about a different chemical.

Where they are.

Nitrosating chemicals and ingredients that are used in personal care are listed below. These ingredients are subject to usage restrictions under the cosmetic product directive and are also monitored by various environmental agencies, government bodies and additional NGO’s.  The following can all produce nitrosamines in certain conditions.




Surfactants containing a nitrogen containing functional group such as those listed above in the patent.


Nitrosamines are also present in tobacco, some meat products (although manufacturers have now found ways to inhibit their formation), YOUR BODY (we make them!) , latex product, pesticides and in drinking water (again, this is monitored and treated).

What do Nitrosamines do?

There is no doubt that nitrosamines are bad for your health. Nitrosamines  are known human carcinogens the link takes you to a report by the US department of health and human services.  However,  the link between cancer and cosmetics containing nitrosamines has not been proved and more research is required and is being carried out.  While it is possible that some cosmetic products may contain nitrosamines, especially as they age, the level of nitrosamine is expected to be extremely low.

What is the cosmetic industry doing about nitrosamines?

The cosmetic industry restricts the amount of nitrosating ingredients that go into personal care products to limit consumer exposure to these bi-products.  Nitrosating ingredients are often only allowed in rinse off products where the skin contact will be fleeting rather than for leave on creams and lotions.  In addition to that there has been much work done on preventing the formation of nitrosamines in formulations. A number of patents exist in this area and ingredients such as squalene and other unsaturated natural oils, ascorbic acid, vitamin E and ascorbyl palmitate may prevent their formation. As mentioned above, the formation of nitrosamines in meat products has been controlled by using similar techniques.

So, what should I do as a consumer?

Well, as you can see above, this area involves quite a bit of chemistry and a fair bit of digging around to get the right information. Over the coming weeks Realize Beauty will outline in more detail the potential  risks associated with each ingredient. In the meantime be assured that the cosmetics industry is actively working towards a nitrosamine free cosmetic world and while working toward that goal, levels of this chemical are being monitored and controlled at levels considered to be safe under normal usage.  Another good resource can be found here: Dermaviduals response to nitrosamine issue.

4 Comments leave one →
  1. March 17, 2009 5:33 pm

    Thank you so much for sharing such valuable information with us. Your blog is very interesting and informative.

  2. RealizeBeautyEd permalink
    March 17, 2009 6:00 pm

    Dear Maria,
    Thanks for your wonderful comments. It is great to have you here with us! Enjoy.

  3. October 1, 2009 6:23 pm

    I don’t know If I said it already but …Great site…keep up the good work. 🙂 I read a lot of blogs on a daily basis and for the most part, people lack substance but, I just wanted to make a quick comment to say I’m glad I found your blog. Thanks, 🙂

    A definite great read..Jim Bean


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