In-depth guide

UPDATED FEB 2026

Hair Relaxer Chemical Exposure

Part of the Hair Relaxer Cancer investigation

The short answer

Hair relaxers contain at least 45 endocrine-disrupting chemicals across 10 chemical classes. 84% of these chemicals are NOT listed on product labels. The chemicals enter the body through the scalp, whose protective barrier is compromised by the relaxing process itself.

People's Justice Research TeamUpdated February 20, 2026Fact-checked

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The Chemical Cocktail in Your Hair Relaxer

Chemical testing has identified at least 45 endocrine-disrupting or asthma-associated chemicals in hair relaxer products, spanning 10 chemical classes: phthalates (estrogen mimics), parabens (estrogen mimics), formaldehyde and releasing agents (carcinogens), bisphenol A/BPA (estrogen mimic), cyclosiloxanes D4 and D5 (endocrine disruptors, suspected carcinogens), heavy metals (lead, mercury, arsenic, cadmium), alkylphenols (estrogenic), glycol ethers (reproductive toxicants), UV filters (endocrine disruptors), and synthetic musks (estrogenic).

The Scalp Absorption Pathway

Hair relaxers work by applying strong alkaline chemicals (sodium hydroxide or calcium hydroxide) to break protein bonds in hair. These same chemicals damage the scalp's protective barrier — the stratum corneum — dramatically increasing percutaneous absorption of co-formulated EDCs. The burning sensation nearly all users experience confirms active barrier compromise. This broken-barrier pathway delivers chemicals directly into the bloodstream at far higher rates than intact-skin application.

The Labeling Failure

Testing found that 84% of EDCs detected in hair products were NOT disclosed on product labels. Consumers had no way to know what chemicals they were absorbing. Products marketed to children ("Just for Me") contained the same undisclosed EDCs. The labeling gap is central to the failure-to-warn claims.

Reducing Your Exposure

If you currently use chemical hair relaxers, consider transitioning to natural hairstyles, protective styles, or heat-based methods that don't involve chemical application. The Sister Study evidence applies specifically to chemical straightening products, not heat-based tools. Reducing frequency of chemical applications reduces cumulative EDC exposure.

Research & evidence

Scientific Evidence

Hair Relaxer Use and Risk of Uterine Cancer in the Black Women's Health Study

Bertrand KA, Coogan PF, Palmer JR (2023). Environmental Research

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Use of Straighteners and Other Hair Products and Incident Uterine Cancer

Chang CJ, O'Brien KM, Keil AP, Gaston SA, Jackson CL, Sandler DP, White AJ (2022). Journal of the National Cancer Institute

View on PubMed

Use of Hair Products in Relation to Ovarian Cancer Risk

White AJ, Sandler DP, et al. (2021). Carcinogenesis

View on PubMed

FAQ

Frequently Asked Questions

36 QUESTIONS

Chemical hair relaxers contain endocrine-disrupting chemicals (EDCs) — phthalates, parabens, formaldehyde, BPA, and cyclosiloxanes — that mimic estrogen when absorbed through the scalp. Chronic estrogen overstimulation promotes abnormal growth in hormone-sensitive tissues. The NIH Sister Study found that frequent relaxer users face a 155% increased risk of uterine cancer and a 119% increased risk of ovarian cancer.

Dive deeper

Related Guides

7 GUIDES

The full investigation

Part of the Hair Relaxer Cancer Investigation