Can hair straighteners and chemical relaxers increase your risk of cancer?

What's actually in it

Hair straighteners and chemical relaxers contain formaldehyde, phthalates, parabens, and other endocrine-disrupting chemicals. These products are applied directly to the scalp, where chemicals can be absorbed through the skin and inhaled as fumes. The scalp has rich blood flow, making it an efficient entry point into the body.

What the research says

A 2026 study in J Natl Cancer Inst tracked users of hair straighteners and chemical relaxers and found that regular use was linked to higher incidence of non-reproductive cancers. The risk increased with more frequent use. The study controlled for other cancer risk factors.

Formaldehyde in straightening products is a known carcinogen. Heat from flat irons and blow dryers can increase chemical release from treated hair. People who straighten their hair weekly face the highest cumulative exposure.

Choose "formaldehyde-free" straightening treatments and verify the claim with the ingredient list. Consider reducing the frequency of chemical treatments. Use heat tools on lower settings to minimize chemical off-gassing from treated hair.