Difference between Sodium Lauryl Sulphate & Ammonium Lauryl Sulphate

Although Sodium lauryl sulphate (SLS) and Ammonium lauryl sulphate (ALS) have similar sounding names and are both classed as anionic surfactants, they have very different molecular structures. SLS is a comparatively simple molecule and is therefore quite small in size. This gives it the ability to penetrate the outer layers of the skin, particularly when used in conditions which encourage the skin's pores to open, such as when in a warm bath or shower. When SLS penetrates the outer layers of the skin in this way, it comes into contact with more delicate cells that are in the process of being formed in the dermis. It is here that the irritation associated with SLS manifests itself, resulting in reddening and erythema of the skin.

ALS, by contrast, is a far more complex molecule and is physically much larger. This means that it is practically impossible for ALS molecules to penetrate the outer layers of the skin and so reach the delicate underlying layers of cells. Due to this difference, ALS is regarded as being considerably less irritating than SLS - on a scale of 0 to 10, where the potential irritancy of water is 0 and that of SLS is 10, ALS scores around 4 - clearly far less irritating than SLS.

It should perhaps be pointed out at this stage that ALL surfactants or foaming agents have the potential to irritate the skin, regardless of their name, source or claims made for them. This is simply because of the way they work - if you want a shampoo or shower gel to cleanse the skin and produce foam or bubbles, then you have to accept that the product will have the potential to cause irritation.