By: Madison Bruner

Although the beauty industry thrives on creativity and artistry, few consumers would risk their lives or health for glamour. In early 2025, three hairstylists filed lawsuits in California against L’Oreal, Wella, Redken, and Paul Mitchell, alleging that these beauty giants and others sold products with carcinogenic chemicals that caused bladder cancer, without providing consumers any warning of the associated risks.

The complaints for the lawsuits can be viewed below:

1. Hector Corvera v. L’Oreal USA Inc. et al filed on February 13, 2025;
2. Debra Matarazzo v. Henkel AG & Co. KGaA et al filed on March 6, 2025; and
3. Sharon Mirtaheri v. L’Oreal USA Inc. et al filed on April 28, 2025.

Breaking Down the Lawsuits Against L’Oreal, Wella, Redken, Paul Mitchell, and Procter & Gamble

The primary health concern underpinning these lawsuits is an alleged increased risk of developing bladder cancer associated with the long-term use of hair dye products. The plaintiffs filed a civil suit in the state of California alleging products liability claims such as failure to warn, design defect, breach of warranty of merchantability, and various negligence claims. California’s robust consumer protection laws and a strong unfair competition statute (California Unfair Competition Law) give the plaintiff hairdressers powerful tools to pursue legal remedies.

Failure to Warn – Strict Liability

Manufacturers have a legal duty to warn consumers about potential health risks. The defendants are accused of failing to provide adequate warnings about the carcinogenic chemicals in their products. To prevail on a failure to warn theory a plaintiff must show: (1) The product had potential risks known or knowable at the time of manufacture; (2) The manufacturer failed to adequately warn of those risks; (3) The lack of warning rendered the product dangerous beyond an ordinary user’s expectations; and (4) The inadequate warning was a substantial factor in causing injury.

Design Defect – Strict Liability

The defendants are accused of defective design of their hair dye products. The plaintiffs argue both a risk-utility theory (that feasible alternatives existed through botanical or amine-free formulas) and a consumer-expectations theory (that no consumer expects to get cancer from a hair dye). The plaintiffs further argue that the hair dye formulations, including the “ammonia-free” or “natural” lines contain known carcinogens that defendants could have eliminated without sacrificing function. 

A risk-utility test requires the plaintiff to show whether a reasonable person would determine that the probability of harm of the product will outweigh the burden or costs of taking precautions. Similarly, through the consumer allegation test, plaintiffs must show whether a reasonable person would consider the product defective. 

Negligence

The defendants are accused of both negligent failure to warn and gross negligence. For a negligent failure to warn claim, a plaintiff must show: (1) Defendant owed a duty to warn foreseeable users; (2) Defendant breached that duty by failing to provide adequate warnings; (3) The breach was a proximate cause of injury; and (4) Damages resulted. Gross negligence is a heightened degree of negligence and requires showing “conscious disregard” for safety.

Breach of Warranty

The defendants are accused of breach of warranty, which occurs when a seller “fails to live up to the promises or guarantees they made about a product or service.” A breach of warranty can be expressed or implied. The plaintiffs broadly allege breach of warranty, meaning both express and implied breach of warranty is argued. Specifically, the plaintiffs claim that marketing materials and labels represented the dyes as safe, gentle, or even condition-protective, yet the products caused cancer.

Deceit by Concealment

The defendants are accused of deceit by concealment, with allegations that the defendants actively concealed known carcinogenic ingredients such as aromatic amines. The plaintiffs also allege the defendants lobbied to keep safety data from regulators. This suppression induced stylists to continue using the products, causing injury. Deceit by concealment requires a showing that the defendant conceals or suppresses a material fact, with knowledge of its falsity, intending to defraud, and the plaintiff justifiably relies on that fact. 

Fraud

Finally, the defendants are accused of fraud, as the plaintiffs allege that the defendants misrepresented on packaging and in advertising that the dyes were “safe” or “damage-free,” and did so knowing those representations were false. A claim of fraud requires the plaintiff to show: (1) A false representation of a material fact; (2) Defendant’s knowledge of its falsity; (3) Intent to induce reliance; (4) Justifiable reliance by plaintiff; and (5) Resulting damage.

Violations of CA Unfair Competition Law

Cal. Bus. & Prof. Code § 17200 prohibits “any unlawful, unfair or fraudulent business act or practice.” Firstly, the plaintiffs allege that the defendants’ conduct was unlawful by violating FDA labeling regulations requiring warnings on cosmetics. Secondly, the plaintiffs alleged unfair practices, that the defendants concealed known hazards while continuing to market dyes as safe. Finally, plaintiffs allege fraudulent activity, claiming that defendants misled consumers about safety and ingredient risks.

Scientific Studies Linking Hair Dye to Cancer

Multiple studies have confirmed the potential link between hair dye and cancer. A 2019 study reported higher instances of breast cancer among women who use permanent hair dye, as well as chemical straighteners. Studies finding statistically significant links with hair dye use by hairstylists and bladder cancer go back many years, with research displaying hairdressers of 10+ years were nearly twice as likely to develop bladder cancer versus those who had never worked as a hairdresser.

However, research results are mixed; a 2022 study conducting a systematic review of studies from 2000-2021 indicated that only one of the four studies found an increased risk of bladder cancer for hairdressers as compared to population controls. Regardless, the hair dye lawsuits stand on legitimate scientific evidence, and manufacturers, regulators, and consumers should take the claims seriously..

Behind the Formulas: Understanding the Alleged Carcinogens

Given there is a real risk of adverse health effects with long-term use of hair dye products, let’s break down the key chemicals you need to know about.

1. 4-Aminobiphenyl (4-ABP): Classified by IARC as a Group 1 (“carcinogenic to humans”) bladder carcinogen and by the NTP as “known to be a human carcinogen.” Studies have repeatedly detected 4-ABP in commercial hair dyes and in DNA adducts in bladder tissue, linking it mechanistically to bladder cancer via metabolic activation to a reactive nitrenium ion that binds DNA.
2. Ortho-Toluidine (o-Toluidine): IARC Group 1 and NTP “known human carcinogen.” O-Toluidine forms DNA adducts in bladder tissue through metabolic conversion to N-hydroxy-o-toluidine, causing mutations on prolonged exposure.
3. Benzidine (and benzidine-metabolites): A long-banned industrial dye still detected in some formulations. IARC lists benzidine as a Group 1 bladder carcinogen; metabolized derivatives likewise trigger DNA damage and cancer risk.
4. 2-Naphthylamine: Another IARC Group 1 bladder carcinogen historically used in dyes and still alleged to persist in minor amounts, with strong epidemiological ties to increased bladder-cancer incidence.
5. 4-Chloro-ortho-Toluidine: Classified by IARC as Group 2A (“probably carcinogenic to humans”). Detected in defendants’ dye lines and implicated in bladder-cancer risk.
6. 2,4-Diaminoanisole sulfate (4-methoxy-m-phenylenediamine sulfate): Identified by the FDA and NTP as a carcinogenic dye intermediate that is “reasonably anticipated to be a human carcinogen” and is used to achieve certain permanent-color shades.
7. 2,4-Diaminotoluene and Disperse Blue 1: Both listed by the NTP as “reasonably anticipated to be human carcinogens,” these intermediates remain in some permanent-dye formulations.
8. Basic Red 9 Monohydrochloride and 4,4′-Oxydianiline: Also flagged by the NTP as “reasonably anticipated to be human carcinogens,” used for red and other vivid shades.
9. Coal tars and coal-tar pitches: Classified by the NTP as “known carcinogens” and historically used as dye precursors; they introduce complex mixtures of polycyclic aromatic hydrocarbons linked to cancer.
10. Aniline and Aniline Hydrochloride: IARC Group 2A (“probably carcinogenic to humans”) and noted in occupational-exposure studies; these simple amines persist as minor components in various dye mixes.

Avoiding these listed chemicals is the safest way to minimize your exposure to carcinogens and protect your health. 

‘Natural’ Alternatives: Bona Fide or Bogus?

In response to health and environmental concerns, several hair color brands market themselves as natural, organic, or safer alternatives. A prime example is Aveda, which advertises its professional hair color line as “96% naturally derived” and PPD-free. PPD-free means Aveda products contain no p-phenylenediamine, but the products could still include other problematic intermediates or residues like 4-ABP, o-toluidine, and benzidine. Instead of using the p-phenylenediamine found in typical dyes, Aveda’s formulas use other dye molecules like p-aminophenol and 2,4-diaminophenoxyethanol (along with plant-based ingredients) to achieve color. 

So are these “natural” hair dyes safer? They do eliminate certain known harmful ingredients named in the complaints. For example, Aveda explicitly states it contains no coal-tar ingredients and no petrochemicals, which means it likely avoids the carcinogenic aromatic amines at issue. However, experts caution that “natural” doesn’t mean chemical-free or risk-free. Because these chemicals are newer, there is less research on their long-term health effects compared to the older chemicals.

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