Sodium cocoamphoacetate

What it is

Sodium cocoamphoacetate is an amphoteric (two-charge) surfactant made from coconut fatty acids. In shampoos it is a secondary surfactant that adds foam and mildness, and it is common in gentle and tear-free formulas. A close relative, disodium cocoamphodiacetate, was among the best-tolerated surfactants in a patch-test study (Corazza 2010). That study did not test sodium cocoamphoacetate itself.

How it works

Like other amphoterics, its net charge depends on pH. It packs between anionic surfactant molecules in micelles, lowering their irritation and increasing foam and thickness (Thompson 2023; Cornwell 2018).

What the studies show

• In 105 patients patch-tested with eight cleansing surfactants, none caused irritation or allergic reactions at the tested dilution. The best tolerated were sodium cocoyl glutamate, sodium lauroyl oat amino acids and disodium cocoamphodiacetate, while cocamidopropyl betaine from the standard series gave 5 positives (Corazza 2010). This is a related ingredient, shown only as the closest tested relative.
• A review gives an overview of shampoo surfactant raw materials and the trend toward sulfate-free systems (Cornwell 2018).

We found no hair-specific human trial for this ingredient. Claims about hair feel and dryness come from formulation science and manufacturer material, so the direct evidence is weak.

Side effects and safety

Irritation potential is low for the class. Rare contact allergy has been reported for amphoteric surfactants, with cocamidopropyl betaine the better-known example.

Bottom line

A good sign on the label of a mild or sulfate-free shampoo for dry, curly or sensitive scalps, but it is a supporting actor: the primary surfactant decides cleaning power and mildness. It is not a reason in itself to buy a product. No head-to-head studies against cocamidopropyl betaine for hair or scalp outcomes were found.