Is sodium cocoyl isethionate a sulfate? What sulfate-free actually means

What does sulfate-free mean?

Sulfates are a family of anionic surfactants, sodium lauryl sulfate and sodium laureth sulfate being the famous two. They are cheap, they foam hard, and sodium lauryl sulfate in particular is the standard irritant dermatologists use when they want to damage a skin barrier on purpose in a study. Sulfate-free simply means the cleanser uses a different surfactant family. On its own that tells you nothing about whether the alternative is gentle. Some are, some are not.

Why is sodium cocoyl isethionate mild?

Surfactants clean by forming micelles that carry oil and dirt into the rinse water. The trouble starts when those micelles are small enough to slip into the water-filled pores of the stratum corneum and take skin proteins and lipids with them on the way out. That is the stripped, tight feeling, and it is the start of the whole apology cycle where you then buy a moisturizer to undo your cleanser.

In 2007, Ghosh and Blankschtein measured the micelles. Sodium cocoyl isethionate micelles came out at 33.5 plus or minus 1 angstrom, larger than the 29 plus or minus 5 angstrom average radius of the skin's aqueous pores, so they were sterically hindered from penetrating, and the amount of SCI that penetrated skin did not rise with dose. Too big to get in is the current best explanation for why it reads as mild, and it is a better explanation than a marketing word.

Does pH matter more than the surfactant?

It matters at least as much. The mildness argument for sodium cocoyl isethionate depends on staying near skin's own pH. A review of cleanser technology in Dermatologic Therapy in 2004 found that a pH of 10 alone, with no surfactant at all, increases stratum corneum swelling. Traditional soap sits around that pH. A cleanser can be sulfate-free and still be alkaline enough to do the damage on its own, so the number to look for is a low pH, not an absence of one ingredient.

Why does a mild cleanser still foam?

Because foam and harshness are not the same property. Sodium cocoyl isethionate builds a dense, creamy foam at a skin-friendly pH; it is the ingredient that makes syndet bars behave like soap without behaving like soap. The idea that a gentle cleanser must be a sad, non-foaming milk is a myth that mostly served brands that could not formulate a real foam at low pH.

What about the humectant?

A rinse-off cleanser has seconds of contact time, so what matters is what survives the rinse. Glycerin does. It is a small molecule that binds water in the stratum corneum, and a 2008 review in the British Journal of Dermatology collects decades of data on improved hydration, barrier function and mechanical properties, plus protection against irritating stimuli. In a cleanser it is the difference between clean and clean-but-tight.

What we made with it

Clean Slate is a low-pH gel cleanser for face and body built on sodium cocoyl isethionate with glycerin, and suspended jojoba beads that are there because they are beautiful. It washes, rinses clean and leaves you alone. Step one, morning and night, and the reason the rest of the routine does not have to apologize for the cleanser.

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