The Lab
Specimen No. 0174
AvoidSyntheticskincare

1,4-Dioxane

A carcinogenic manufacturing byproduct that can form during the ethoxylation of foaming agents such as SLS and SLES. It is a contaminant rather than an intentionally added ingredient, so it does not appear on labels.

medium confidence
Researched July 7, 2026

Concerns

  • IARC Group 2B; EPA classifies it as a likely human carcinogen; not disclosed on labels (a processing contaminant); has been detected in roughly 50% of tested personal care products; New York set limits in 2023

Regulatory flags

  • IARC Class: Gr2B
  • EDC Status: None
  • Regulatory: US: no federal limit; NY: limits 2023; EU: trace limits; CA: tracking
  • Evidence Grade: B

Commonly found in

Foaming products (byproduct of SLS/SLES ethoxylation — not a direct ingredient)

Research disclaimer: This rating is based on available peer-reviewed research and regulatory assessments at the time of publication. It is not medical advice. Consult a qualified professional for personal health or skin concerns.

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LabelCleared verdict badge: 1,4-Dioxane — Avoid
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