Surfactants - Does the counterion matter?

There was an interesting discussion on LinkedIn about whether Magnesium Laureth Sulfate was more gentle than Sodium Laureth Sulfate.  It’s a pretty good question and I’m not really sure about the answer.  Here is what my experience has been. 

Sodium and Ammonium

When I formulated at Alberto Culver we used SLS and SLES in our shampoos.  At the time about half of all the top selling shampoos used SLS/SLES.  The other half used ALS/ALES (ammonium lauryl sulfate / ammonium laureth sulfate).  This included brands like Suave, Finesse, and Salon Selectives.  What it really boiled down to was that P&G, who had many of the top shampoos, used SLS/SLES and Helene Curtis, who eventually became Unilever and had many other top shampoos, used ALS/ALES.  Since I worked on the VO5 brand we typically compared our performance to Suave which was similarly positioned.  This was convenient because they used ALS/ALES and we used SLS/SLES.

In all the testing I did there wasn’t much difference in performance.  We were not able to demonstrate any customer preference of the shampoos in home use tests and we couldn’t find any foaming or combing differences in lab tests.  As far as my testing went, I couldn’t tell a difference between the counterion used in the surfactant.    So, at least in my experience, there really is no noticeable performance difference between an ammonium based surfactant and a sodium based one.

As far as irritation goes, the CIR concluded that while both have the potential to be irritating to skin, they can be formulated to be non-irritating.

I would be curious if anyone could direct me to research that shows differently.

Other counterions

In the discussion the original question was about Magnesium Laureth Sulfate.  This isn’t an ingredient I’ve ever used.  It was commonly believed by responders in the thread that MLES is less irritating to the skin than SLES.  However, according to this research ( Paye, Zocchi, Broze XXVII Jornadas Anuales CED Barcelona, Spain, June 1998, pagg.449-456) there is no difference in skin irritation when tested in-vivo on human subjects.

So, I can’t think of any good reason to choose one of these types of surfactants over the other except when it comes to questions of supply and pricing.  The reason we used SLS/SLES was not because it was superior to ALS/ALES.  It was only because we were able to get a better price break on the sodium surfactant.  I suspect that the reason Helene Curtis used ALS was because they got a better price on the ammonium surfactant.

Sometimes that is all it takes to choose one raw material over another.