Encyclopedia · surfactant
Ammonium lauryl sulfate
The ammonium-salt twin of SLS, a strong cleanser with essentially the same cleaning power and irritation profile.
What it is
Ammonium lauryl sulfate (ALS) is lauryl sulfate with an ammonium instead of a sodium counter-ion. Dermatology reviews group it with SLS as a lauryl sulfate primary cleanser: very good at removing sebum, rich foam in hard and soft water, easy to rinse, typically used in shampoos for oily hair and needing a secondary surfactant or conditioner to offset harshness (D'Souza 2015; Gavazzoni Dias 2014).
How it works
The anionic mechanism is the same as for SLS: it adsorbs at oil and hair interfaces, forms micelles and solubilizes sebum (see how shampoo works and sodium lauryl sulfate). The counter-ion changes solubility and thickening more than skin effects. We found no head-to-head human irritation study of ALS versus SLS.
What the studies show
- CIR's earlier assessment of SLS and ALS supplied the data used to clear related alkyl sulfates as safe as used (Fiume 2010).
- A dermatology review lists ALS with SLS as lauryl sulfate primary cleansers for oily hair that leave hair harsh unless conditioned (D'Souza 2015).
- A review and pH survey of 123 shampoos names ALS among the common anionic shampoo surfactants (Gavazzoni Dias 2014).
How it's used in studies
We found no clinical studies of ALS on hair. In formulations it plays the same primary-surfactant role as SLS at similar levels, up to about 10% (Thompson 2023).
Side effects and safety
- Expect SLS-like irritation potential, which depends on dose and contact time. It is not known as a sensitizer.
- It is not ethoxylated, so 1,4-dioxane contamination is not expected (compare ammonium laureth sulfate).
- It is a permitted cosmetic ingredient in the US, EU and UK.
Bottom line
Treat ALS exactly like SLS when choosing a shampoo: an effective, cheap cleanser suited to oily scalps, clarifying washes and heavy product users, and the first thing to avoid if your scalp is sensitive or your hair is dry, curly or colour-treated. Evidence for any ALS-specific benefit or harm is lacking. Marketing sometimes presents ALS as gentler than SLS, and we found no human data comparing them directly.
Studies 4
Fiume M et al. Final report on the safety assessment of sodium cetearyl sulfate and related alkyl sulfates as used in cosmetics. Int J Toxicol. 2010
Result: Cosmetic Ingredient Review assessment that used data from its earlier SLS and ammonium lauryl sulfate reviews to support the safety of related alkyl sulfates as used (0.1-29%, mostly soaps and shampoos).
Read the study ↗D'Souza P, Rathi SK. Shampoo and Conditioners: What a Dermatologist Should Know? Indian J Dermatol. 2015
Result: Dermatology review of shampoo and conditioner ingredients: foam does not equal cleaning, non-ionics are the mildest and weakest cleansers, and saponin-based natural cleansers lather but clean poorly.
Read the study ↗Gavazzoni Dias MF et al. The Shampoo pH can Affect the Hair: Myth or Reality? Int J Trichology. 2014
Result: 38% were at or below pH 5.5 and 62% above; 81% of 26 anti-dandruff shampoos and all children's shampoos were above 5.5 (range 3.5-9.0). Alkaline pH may raise fibre charge, friction and cuticle damage; a measurement and mechanism review, not a wear trial.
Read the study ↗Thompson CJ, Ainger N, Starck P, Mykhaylyk OO, Ryan AJ. Shampoo Science: A Review of the Physiochemical Processes behind the Function of a Shampoo. Macromol Chem Phys. 2023
Result: Reviews how surfactants lift soil from hair (roll-up, emulsification, solubilization), why shampoos pair a primary anionic with an amphoteric co-surfactant, and states that foaming does not affect cleaning. Two authors were from Unilever R&D.
Read the study ↗Related
- 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 laureth sulfateThe ammonium-salt version of SLES, an ethoxylated sulfate cleanser that is gentler than lauryl sulfates and can carry a trace by-product called 1,4-dioxane.
- 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.
- Cocamidopropyl betaineThe most common helper surfactant in shampoo, which makes sulfate cleansers gentler, thicker and foamier, and a rare cause of scalp allergy that usually comes from manufacturing impurities.
- 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.