Reference summary — not medical advice or a personal risk estimate.
Hair conditioner
Post-shampoo hair treatments. Often use the same preservative chemistry as shampoo.
Also known as: leave-in conditioner, hair mask
What this does NOT mean
Finding a factor documented in this product category does not establish that ordinary use of hair conditioner causes cancer. It means research — through regulatory testing, recall records, or IARC review — has found that chemical present in this category. Whether it matters for you depends on formulation, dose, frequency, and route of exposure.
What has been documented
- FormaldehydeIARC Group 1IARC Group 1Byproduct of ingredients · medium confidence
Formaldehyde-releasing preservatives sometimes used.
Evidence source: EPA CPDat
- 1,4-DioxaneIARC Group 2BIARC Group 2BContamination · medium confidence
Trace contaminant from ethoxylated surfactants; concentration falls below detection when good manufacturing practices are followed.
Evidence source: US EPA
How to read this page
A factor appearing on this page means it has been documented in this product category — through EPA / FDA testing, IARC monographs, or regulatory recall records. Whether it presents a meaningful personal risk depends on the specific formulation, dose, and how you're exposed. Click any factor to read what science actually says about it, and where.