1,4-dioxane is a trace byproduct that can form during ethoxylation — the chemical step that turns lauryl alcohol into the ethoxylated alcohol used to make SLES. It is never added intentionally; it is a process contaminant, and only ethoxylated materials (like SLES) are affected. SLS, which is not ethoxylated, does not carry this concern.
Why buyers care:
- Several markets set explicit limits or monitoring expectations for 1,4-dioxane in finished cosmetic products.
- Retail and brand "clean" standards increasingly ask for documentation on it.
The good news: controlling it is standard industry practice. Reputable producers remove 1,4-dioxane by vacuum stripping during manufacture and confirm the level by batch testing. Your job as a buyer is simply to ask for the number — a maximum limit on the specification sheet, backed by batch data on the COA. A professional supplier answers this question immediately.
See what else belongs on an SLES specification in our SLES 70% buyer’s guide, or request our SLES specification and COA sample.