Are Sulfates
Actually Toxic?

What SLS and SLES are

SLS and SLES are anionic surfactants: molecules with a water-loving head and an oil-loving tail, the same basic mechanism behind essentially every cleanser, from dish soap to shampoo. That structure is what lifts oil and residue off the scalp and hair and carries it away in the rinse water.

SLES is the ethoxylated version of SLS — an extra manufacturing step adds ethylene oxide units to the molecule before it’s converted to a sulfate. That step is why the two behave differently on skin, and why they shouldn’t be treated as interchangeable even though they’re usually mentioned in the same breath.

Both are inexpensive, produce a dense, immediately recognisable lather, and clean effectively, which is why they have been the default choice in mass-market shampoo for decades.

Where the evidence for irritation is real

SLS is a genuinely well-studied irritant — so well-characterised that dermatology uses it as a reference irritant in patch testing, precisely because its effect on the skin barrier is so reliably reproducible. At higher concentrations, and especially with prolonged or repeated contact, it can strip natural oils and irritate skin and eyes more than milder surfactants do. People with eczema, psoriasis, or an already-compromised skin barrier tend to notice this more than others.

SLES exists partly to address that: the ethoxylation step makes it milder and less irritating than SLS in rinse-off use. The trade-off sits on the manufacturing side rather than the use side — ethoxylation can leave trace amounts of 1,4-dioxane as a processing by-product if the raw material isn’t properly purified afterward. That is a quality-control question tied to how a given batch of SLES was made, not an inherent property of the ingredient, which is why regulators set limits on it and why reputable suppliers test for and remove it.

Where the "toxic" claim breaks down

Neither the EU’s Scientific Committee on Consumer Safety (SCCS) nor the US Cosmetic Ingredient Review (CIR) panel — the two bodies that actually evaluate cosmetic ingredient safety data — classify SLS or SLES as carcinogenic or systemically toxic at the concentrations and contact times used in rinse-off products like shampoo. Both are considered safe for that use. What tends to get lost in the online alarm around sulfates is the difference between irritation potential and toxicity: SLS can irritate skin at certain concentrations, particularly with prolonged contact — that is real and documented. It is not the same claim as "carcinogenic" or "toxic," and the data doesn’t support that stronger claim.

Our shampoo is sulfate-free regardless, built on a milder SCI + CAPB base — and on Bồ Kết’s own saponins, which contribute genuine surfactant activity in their own right rather than standing in for a harsher cleanser. That’s a formulation choice, not a safety claim about sulfates. See Why your shampoo’s surfactant system matters more than you think for the full breakdown of that system.