The science
The interesting chemistry in this wash is the surfactant system, and it deserves to be read as a system rather than as four separate molecules. Lauroyl/myristoyl methyl glucamide belongs to the N-methyl glucamide family, sugar-headed nonionic surfactants that have been studied since the 1990s as low-irritation alternatives to alkyl sulfates; in comparative patch and wash tests glucamides consistently remove less stratum corneum lipid and produce less transepidermal water loss than sodium lauryl sulfate at equivalent cleaning. Sodium cocoyl isethionate brings the dense, cushioned lather and was the surfactant that made the original syndet bar possible; it is anionic but with a low critical micelle concentration and a well-documented mildness profile. The glycinate and cocamidopropyl betaine sit alongside as secondary surfactants, and the betaine in particular is known to reduce the irritation of anionic surfactants when blended with them, which is the reason it appears in almost every sulfate-free wash on the market. Together this is a textbook mild blend, and its mildness is the sole mechanistic basis for the moisturizing claim: it takes less, so skin is left with more.
What the formula does not do is deposit. Glycerin is a humectant and is present at a reasonable level, but rinse-off delivery of humectants is poor; deposition studies of glycerin from cleansers show only marginal residual hydration compared with leave-on application. Coconut oil, the marketed hero, is far down the list, and although coconut oil has a genuine literature as a leave-on emollient, including a randomized trial in mild-to-moderate xerosis published in Dermatitis in 2004 showing it performed comparably to mineral oil, that evidence concerns a leave-on oil at full concentration, not a trace in a wash. The silky after-feel is more plausibly explained by polyquaternium-7, a cationic conditioning polymer that adsorbs to skin during rinsing via the same mechanism it uses on hair.
The preservative system is the one place where the evidence cuts the other way. Methylchloroisothiazolinone and methylisothiazolinone are effective broad-spectrum preservatives, but the isothiazolinone allergy epidemic of the 2010s is well documented in the contact dermatitis literature, and although rinse-off exposure carries much lower risk than leave-on, it is not zero for already-sensitized individuals. No clinical testing has been published on this specific wash.
References 1 ShowHide
- A randomized double-blind controlled trial comparing extra virgin coconut oil with mineral oil as a moisturizer for mild to moderate xerosis — Dermatitis (2004)