Encyclopedia · surfactant
Sodium C14-16 olefin sulfonate
A sulfonate-based cleanser common in sulfate-free shampoos that is still a strong degreaser, so sulfate-free does not always mean gentle.
What it is
Alpha-olefin sulfonates are made by sulfonating 14- to 16-carbon olefins. They are sulfonates, not sulfates, so shampoos containing them can be labelled sulfate-free, but in practice they clean about as vigorously as sulfates and tolerate hard water well.
How it works
It forms anionic micelles like the sulfates (see how shampoo works).
What the studies show
We found no human scalp or hair evidence. Our search returned only a 1977 rat study of skin absorption of alpha-olefin sulfonate, which we read at abstract level only (Minegishi 1977). A review gives an overview of shampoo surfactant raw materials and the trend toward sulfate-free systems (Cornwell 2018). Claims about hair feel come from formulation science and manufacturer material.
Bottom line
Do not assume "sulfate-free" means gentle when the primary surfactant is an olefin sulfonate. It is fine for oily scalps, but for dry or curly hair check the rest of the formula. Comparative irritation and hair-lipid-loss data against SLES are needed.
Studies 2
Minegishi KI et al. Percutaneous absorption of alpha-olefin sulfonate (AOS) in rats. 1977
Result: Study of skin absorption of alpha-olefin sulfonate in rats; read at abstract level only.
Read the study ↗Cornwell PA. A review of shampoo surfactant technology: consumer benefits, raw materials and recent developments. Int J Cosmet Sci. 2018
Result: Overview of shampoo surfactant raw materials, consumer benefits and trends in sulfate-free systems.
Read the study ↗Related
- Sodium laureth sulfateThe workhorse cleanser of mainstream shampoos, SLS with a short ethylene-oxide chain added, which keeps most of the cleaning and foam and is gentler, with a trace by-product called 1,4-dioxane.
- Sodium lauryl sulfateA cheap, strong cleanser and foamer that removes oil very well but is the most irritating common shampoo surfactant, so dermatologists use it as their standard test irritant.
- Ammonium lauryl sulfateThe ammonium-salt twin of SLS, a strong cleanser with essentially the same cleaning power and irritation profile.
- How shampoo worksShampoo is water plus a blend of cleansing molecules that lift oil off your scalp and hair, and the blend matters far more than any single label word.