Sodium Alpha Olefin Sulfonate

What It Is

Sodium alpha olefin sulfonate (AOS) is an anionic surfactant produced from alpha olefins, which are typically derived from coconut oil or palm kernel oil (CAS 68439-57-6). Despite the word "sulfonate" in its name, AOS is not a sulfate — it belongs to a different chemical class. Its primary function is as a high-foaming primary cleanser in liquid soaps and detergents.

Common Uses

AOS is commonly found in liquid hand soaps, dish soaps, body washes, shampoos, and bubble bath formulations. It is frequently chosen as the primary surfactant in products marketed as sulfate-free, because it provides strong foam and cleaning performance comparable to sodium lauryl sulfate (SLS) without the sulfate chemistry. It is less common in hard-surface cleaners, where nonionic surfactants tend to dominate.

How It Works

As an anionic surfactant, AOS carries a negative charge on its head group when dissolved in water. This charge helps it interact strongly with positively charged dirt and grease particles, lifting them away from skin or dish surfaces. Its molecular structure produces dense, stable foam — more so than most nonionic surfactants — which is why it works well as the lead cleanser in products where visible lather matters to the user.

AOS is also highly water-soluble and rinses cleanly without leaving residue. Compared to SLS, AOS is generally considered milder on skin, though both are anionic surfactants and can cause irritation at high concentrations. In practice, AOS is almost always blended with milder co-surfactants (like cocamidopropyl betaine or decyl glucoside) to reduce irritation potential while maintaining cleaning power.

Safety and Regulation

The Cosmetic Ingredient Review (CIR) Expert Panel has reviewed alpha olefin sulfonates and concluded they are safe as used in cosmetics when formulated to be nonirritating (CIR, 1999; re-reviewed 2017). AOS has low acute oral toxicity and is not classified as a carcinogen, mutagen, or reproductive toxicant by major regulatory bodies.

Like most anionic surfactants, AOS can cause skin irritation at high concentrations or with prolonged, undiluted contact. In finished consumer products at typical use concentrations (generally 5–15% in liquid soaps), irritation is mitigated by dilution, rinsing, and the presence of co-surfactants and conditioning agents in the formula.

AOS is readily biodegradable. Unlike sodium laureth sulfate (SLES), it is not produced through ethoxylation and therefore does not carry the risk of 1,4-dioxane contamination as a processing byproduct.

Why Natural Flower Power Uses It

Natural Flower Power uses sodium alpha olefin sulfonate as the primary surfactant in its hand soaps and dish soaps.

AOS is the first ingredient after water in both formulas, which means it does most of the heavy lifting on cleaning and foam. We needed an anionic surfactant strong enough to cut grease on dishes and produce the kind of lather people expect from a hand soap — but without using sulfates. AOS fit that requirement. It generates rich, stable foam, rinses clean, and pairs well with the cocamidopropyl betaine and decyl glucoside we use as co-surfactants.

The tradeoff with AOS is that it is more drying to skin than a pure nonionic surfactant like decyl glucoside would be on its own. That is why our hand soap formula includes vegetable glycerine, aloe vera, and vitamin E — they offset the stripping effect and keep hands feeling soft after washing. In the dish soaps, where skin contact is shorter and grease-cutting matters more, the balance shifts toward cleaning power.

Related Ingredients

Sodium lauryl sulfate (SLS) is the most commonly compared anionic surfactant — similar foam and cleaning power, but classified as a sulfate with a different irritation profile. Sodium laureth sulfate (SLES) is an ethoxylated version of SLS, milder but with potential 1,4-dioxane contamination concerns. Cocamidopropyl betaine and decyl glucoside are milder co-surfactants that Natural Flower Power blends with AOS to balance cleaning power and skin gentleness.

Sources

• Cosmetic Ingredient Review (CIR). "Final Report on the Safety Assessment of Sodium Alpha-Olefin Sulfonates." International Journal of Toxicology, 1999; re-reviewed 2017.