Key takeaways
- Anionic surfactants clean well and irritate most; amphoterics are milder and foam less.
- A mild system pairs a high-foaming anionic with an amphoteric or nonionic.
- Micellar cleansers use a very low surfactant dose with a solubiliser.
A cleanser is a surfactant system in water, and the system decides almost everything: how much oil it removes, how much it foams, how it feels, and how much of the skin’s own lipid it takes with it. The foam is the least useful indicator and the most heavily marketed.
1. Anionic surfactants
Sodium lauryl sulfate cleans strongly, foams well and irritates at typical doses. Sodium laureth sulfate is milder and is the workhorse of the category. Amino acid surfactants such as sodium cocoyl glycinate are milder still and cost more.
2. Amphoteric surfactants
Cocamidopropyl betaine is the standard secondary surfactant: it improves foam, reduces the irritation of the anionic partner and costs little. It is also a known allergen at higher doses, which is why most formulas cap it at 3 to 5 percent.
3. Nonionic surfactants
Glucosides such as coco-glucoside are mild, foam moderately and are often used in baby and sensitive-skin products. They are less efficient at removing oil, which is an advantage for a morning cleanser and a weakness for a makeup remover.
4. The mild blend
The standard mild system is an amino acid anionic at 5 to 10 percent with an amphoteric at 3 to 5 percent, plus a small amount of a nonionic for foam quality. This blend cleans adequately and leaves the skin feeling less tight than a sulfate system at the same active level.
5. Total active matter
Total surfactant active matter, not the percentage of the raw material, determines the cleansing strength. A 12 percent active system is a strong cleanser; an 8 percent system is a mild one. Labels usually show the raw material percentage, which is higher and less informative.
6. pH
Cleansers sit at pH 4.5 to 6 in the mild category. Amino acid surfactants need an acidic pH to stay soluble, which conveniently lands in the skin-compatible range. A sulfate system at pH 7 strips more, partly because of the pH.
7. Micellar systems
A micellar water uses 1 to 3 percent surfactant above its critical micelle concentration, plus a solubiliser, in water. It removes makeup without foaming and without rinsing. The mildness comes from the low dose, and the cleaning power comes from the solubiliser choice.
8. Thickening
Surfactant systems are thickened with a salt, a fatty alcohol or a polymer. Salt thickening works for sulfate systems and fails for amino acid systems, which need a different approach. A cleanser that will not thicken is usually a system mismatch rather than a bad thickener.
9. Test methods
Mildness is measured with corneometer and TEWL readings after repeated washing, or with a patch test under occlusion. Foam height is measured with a blender or a Ross-Miles apparatus, and it tells you about the experience rather than about the mildness.
10. Claims
“Sulfate-free” is a factual claim if no sulfate is present. “Gentle” needs panel or instrument data. “pH-balanced” is meaningless without the number. The claims that survive scrutiny are the ones tied to a measured property.
11. Where it fits
Cleansers sit in the cleanser range; the anhydrous alternative continues in the anhydrous entry.
Reference: Cleanser development records and corneometer panel data, 2025
