ABSTRACT
In the scientific literature, sodium lauryl sulfate (SLS) is regularly used as the ‘‘gold’’ model to induce skin irritation [1]. This is for several reasons:
1. SLS is classified as a skin irritant, Xi-R38 [2], 2. SLS can be obtained in a very pure form, which allows different laboratories
to work on the same material, 3. SLS can be easily formulated in various vehicles, 4. Although a few cases were reported [3], allergic reactions to SLS are not fre-
quent, and 5. The level of induced irritation can be more or less controlled by adjusting the
concentration [4,5], and any skin damage is rapidly reversible. However, SLS is not the only surfactant to be an irritant to the skin, and even if some surfactants are not classified as such by the Dangerous Substances Directive [2], in certain conditions and concentrations all surfactants can be regarded as potential irritants to different degrees. This paragraph will, however, mainly focus on anionic surfactants, as they are mostly used in toiletries and require the most attention in order to optimize their skin compatibility in finished products.
