Sodium Cocoyl Isethionate
In plain terms
A mild, coconut-derived cleanser nicknamed baby foam for its gentleness. It makes the creamy lather in syndet bars and sulfate-free washes, and unlike SLES it is not ethoxylated, so it carries no 1,4-dioxane worry.
What the evidence shows
Sodium cocoyl isethionate, or SCI, is the workhorse of mild cleansers, made from coconut fatty acids joined to isethionic acid. It produces a rich, creamy foam even in hard water while being much gentler than sulfates like SLS. Laboratory work explains why: its cleansing clusters are too large to slip into the tiny pores of the outer skin, so it cleans without stripping the barrier the way smaller, harsher surfactants do. The CIR panel rates it safe when formulated to be non-irritating, and it is not a sensitizer or phototoxic; like most surfactants it can sting eyes at high concentration, while in a finished cleanser it is gentle. It is also fully biodegradable. On the chemistry that matters for clean-label shoppers: SCI itself is not an ethoxylated ingredient, so it does not carry the 1,4-dioxane that can come with sulfates like sodium laureth sulfate or with PEG compounds. One nuance for transparency: a building block used to make SCI is produced with ethylene oxide, which is why SCI cannot be certified organic under COSMOS, but that upstream step does not put 1,4-dioxane into the finished surfactant. The main caution is for the people who make products, not those who use them: the raw powder is a respiratory irritant that needs care when handled.
On the label
Listed as sodium cocoyl isethionate or SCI. A good pick if you want a gentle, sulfate-free cleanser. Nothing to avoid for most skin; if a bar or wash ever feels drying, it is usually the rest of the formula, since SCI itself is mild.