OGX and TRESemmé were sued over a shampoo preservative that releases formaldehyde

Johnson & Johnson and Unilever have both been sued over the same preservative, in two different shampoo lines, over the same allegation: that it leaches formaldehyde onto the scalp and causes hair loss. Neither case has gone to trial. Both are still active. And the ingredient at the center of them is still legal, in the US, at concentrations up to 0.6 percent, with no warning label required.

That is one chemical. There is a second one in the same bottle that nobody sued anybody over, because nobody has to put it on the label at all — and it is the one California just opened a formal rulemaking on, in January 2026, to restrict.

The lawsuits

OGX. Carr v. Johnson & Johnson Consumer Inc., filed in the Southern District of New York, alleges that OGX shampoos and conditioners containing DMDM hydantoin caused hair loss and scalp injuries in people who used them as directed. The complaint says J&J knew about formaldehyde-releasing preservatives well before this — the company had announced in 2012 that it would remove formaldehyde-releasing ingredients from its products by 2015 — but the commitment didn't carry over when J&J acquired Vogue International, and the OGX line with it, in 2016. In 2023, a federal court declined to strike the class allegations, allowing the case to proceed. A separate, earlier OGX suit (Whipple v. Johnson & Johnson) was dismissed with prejudice in 2022 and did not produce a consumer claims process.

TRESemmé. Unilever is fighting this fight on two fronts at once. The older one, Castillo v. Unilever United States, Inc. (No. 1:20-cv-06786, N.D. Illinois), is a consolidated class action over TRESemmé's keratin-line shampoos making the same core claim: DMDM hydantoin breaking down and releasing formaldehyde, causing scalp irritation and hair shedding. As of April 2025 the court had not yet ruled on class certification and no trial date had been set. Then, on July 14, 2026 — five weeks before this was published — six women filed a fresh, separate suit against Conopco Inc. (Unilever's US subsidiary) in the U.S. District Court of New Jersey, alleging Unilever "has known since at least late 2012" that DMDM hydantoin causes hair loss and scalp injury and failed to warn users. Both cases point back to the same earlier episode: a 2012 class action over Unilever's Suave Professionals Keratin Infusion kit, which the company recalled and settled for $10.2 million in 2014 — while continuing to use the same preservative class in TRESemmé for another eight years. Unilever announced in 2021 that it would reformulate to remove formaldehyde-releasing preservatives, and TRESemmé products sold in the US have not listed DMDM hydantoin since mid-2022; the company did not recall product already on shelves or in homes at that time.

Two points worth being straight about: these are allegations, not verdicts, and no monetary judgment has been entered in either case. But both companies had, before the lawsuits, already told the public they intended to move away from this exact chemistry — which is a different thing than a plaintiff's lawyer's claim, and worth weighing on its own.

What DMDM hydantoin actually is

DMDM hydantoin and quaternium-15 are the two most common members of a preservative family called formaldehyde releasers, which also includes imidazolidinyl urea, diazolidinyl urea, and a handful of others. They don't contain formaldehyde as a finished ingredient — they slowly decompose in the presence of water and release small amounts of it over the life of the product, which is the point: it keeps mold and bacteria from growing in a bottle that sits open in a wet shower for months.

The tradeoff is that this is also how you get exposed to it. A 2010 study in Contact Dermatitis found DMDM hydantoin and quaternium-15 among the most frequently positive allergens at patch-test clinics, with reaction rates tracking how long the product sits on skin — rinse-off products like shampoo release less than leave-on ones, but not none. A more recent quantitative risk assessment published in 2023 modeled dermal sensitization risk specifically from DMDM-hydantoin shampoo at typical use concentrations, rather than assuming risk from the ingredient's presence alone — the kind of dose-based analysis this category of claim usually skips.

Formaldehyde itself is classified by the International Agency for Research on Cancer as a Group 1 human carcinogen, meaning the evidence for causing cancer in humans is considered sufficient — specifically nasopharyngeal cancer, confirmed in IARC's 2006 review, and leukemia, added in 2009. It is important to say exactly what that evidence is built on: occupational and industrial cohorts with sustained inhalation exposure — funeral home workers, particleboard manufacturing, embalming. That is a different exposure route, a different dose, and a different tissue than trace formaldehyde rinsed off a scalp in the shower. The lawsuits above allege contact dermatitis and hair-follicle damage, not cancer, and that is the allegation the evidence at the individual-product level actually supports.

Where the two sides of the Atlantic disagree

The US baseline for cosmetics regulation is still mostly the Federal Food, Drug, and Cosmetic Act of 1938, which does not require a cosmetic to be tested, reviewed, or approved before it goes on shelves. The Modernization of Cosmetics Regulation Act of 2022 (MoCRA) — the first real update to that framework in 80-plus years — added facility registration, mandatory recall authority, adverse-event reporting, and a requirement that companies keep records substantiating a product's safety. It did not ban DMDM hydantoin, quaternium-15, or formaldehyde itself, and it did not create a warning-label requirement for any of them.

The EU has gone further, in stages. Quaternium-15 has been banned outright in EU cosmetics since 2017. DMDM hydantoin is still permitted, capped at 0.6 percent. And as of Commission Regulation (EU) 2022/1181, any finished product that releases formaldehyde above 0.001 percent (10 ppm) — down from the old 0.05 percent (500 ppm) threshold — must now carry the words "releases formaldehyde" on the label. Manufacturers had until July 2024 to reformulate or relabel, and a sell-through window for old stock that expired July 31, 2026 — three weeks before this was published. The stricter standard is not an upcoming change anymore; it is now the fully enforced rule across the EU.

No formaldehyde-releaser warning label exists on US shelves, at any threshold, because nothing requires one.

The chemical that isn't even supposed to be there

DMDM hydantoin is at least on the ingredient list. The second chemical worth knowing about isn't, because it was never added on purpose.

1,4-dioxane is a byproduct of ethoxylation — the manufacturing process used to make harsh sulfate detergents like sodium lauryl sulfate gentler, turning them into sodium laureth sulfate (the "eth" is the tell). Ethoxylation can leave trace 1,4-dioxane behind in the finished surfactant unless the manufacturer takes an extra purification step to strip it out. Because it's a manufacturing contaminant and not an ingredient anyone deliberately formulated in, FDA does not require it to appear on the label at all — the one chemical in this story you cannot check for by reading.

The FDA has monitored it periodically since 1981, and its own historical surveys show the trend moving in the right direction: average concentrations in finished cosmetics fell from about 50 ppm in 1981 to about 19 ppm by 1997, and lower still by a 2008 survey using a more sensitive 1 ppm detection limit. That's real progress, driven by manufacturers voluntarily purifying their surfactants — but "voluntary" and "declining average" both mean some products still test high, and there's no federal ceiling forcing all of them down.

1,4-Dioxane is classified by IARC as Group 2B, possibly carcinogenic to humans, and the EPA calls it a probable human carcinogen — both based on liver and nasal tumors in rodents given very high doses in drinking water, not on human epidemiological data, which existing small studies haven't been able to establish either way. That's a real hazard signal and a genuinely weaker one than formaldehyde's Group 1 status; the two chemicals in this article are not equally well-established risks, and treating them as identical would be dishonest.

New York has already set a legal limit. Under amendments to the state's Environmental Conservation Law, shampoo — explicitly named as a "personal care product" in the statute — has been capped at 2 ppm of 1,4-dioxane since December 31, 2022, and at 1 ppm since December 31, 2023. Manufacturers could apply for temporary waivers while working to reformulate; those waivers stopped being valid on December 30, 2025. As of eight months ago, every shampoo sold in New York State is legally required to be at or under 1 ppm, full stop.

California is one step behind, moving now. On January 16, 2026, the state's Department of Toxic Substances Control opened a rulemaking to list shampoo and manual dish detergent containing more than 1 ppm of 1,4-dioxane as "Priority Products" under its Safer Consumer Products program — the same regulatory tool the state uses to force reformulation of other chemicals of concern. DTSC's own rationale points at standard wastewater treatment not removing 1,4-dioxane, meaning it passes through and re-enters water supplies, on top of direct skin and inhalation exposure during a shower. The agency modified the proposal on April 24, 2026, and the public comment period on the revised rule runs through May 11, 2026. This is not law yet. It is a live, contested proceeding, and it could still change before anything is finalized.

The part where we don't oversell it

Sulfates themselves — sodium lauryl and laureth sulfate, the detergents that make shampoo foam — are not the carcinogen story. They're a mundane one: they're strong surfactants that strip natural sebum along with dirt, which is why dermatologists frequently point people with dry, color-treated, or sensitized scalps toward sulfate-free formulas. That's a comfort and hair-texture issue for most people, not a toxicology one, and it's worth not conflating with the dioxane question just because the two ingredients are chemically related.

The "fragrance" listed on most shampoo bottles carries its own separate disclosure gap — one word standing in for what can be dozens of unlisted compounds, protected as a trade secret under 21 CFR 701.3(a). We covered that mechanism in detail, including MoCRA's still-stalled fragrance-allergen rule, in what is actually in your perfume — it applies exactly the same way to a scented shampoo.

And on parabens, which show up in some (not most current mainstream) shampoo formulas: Darbre et al.'s 2004 study found parabens in the majority of breast tumor tissue samples tested, and later lab work has shown they can weakly mimic estrogen and interfere with estrogen-metabolizing enzymes. The EU has responded by banning five parabens outright and capping propyl- and butylparaben at 0.14 percent, banned entirely from leave-on products for children under three. The US has not restricted parabens at any concentration — FDA's position is that current typical exposure levels don't show a demonstrated safety problem. Those are two different regulatory judgment calls on the same data, not a case where one side has evidence and the other doesn't.

What to actually check

You cannot check for 1,4-dioxane on a label — it isn't required to be there. But you can check for what tends to travel with it and around it:

1. Scan the preservatives. DMDM hydantoin, quaternium-15, imidazolidinyl urea, and diazolidinyl urea are the formaldehyde releasers to know. If a brand reformulated because of a lawsuit or public pressure — TRESemmé since mid-2022 is a documented example — that's a real, verifiable change, not marketing.
2. Ethoxylated surfactants are the dioxane risk, not sulfates broadly. Look for "sodium laureth sulfate," "PEG," or any ingredient with "-eth-" in the name. Sodium lauryl sulfate (no "eth") is not ethoxylated and doesn't carry this specific risk, even though it's the harsher detergent of the two.
3. A brand that publishes a 1,4-dioxane certificate of analysis is telling you something a marketing claim can't. "Sulfate-free" is not the same claim as "tested under 1 ppm dioxane" — plenty of sulfate-free products have never been tested for it at all.
4. New York's 1 ppm rule is a genuine national floor for any brand that sells there, which in practice is most national brands. It is the closest thing to an enforced federal standard this category currently has.

This is exactly the gap Tallow exists to close — scanning a barcode and surfacing what's actually in a product, ingredient by ingredient, with the published lab results and regulatory record attached instead of a marketing claim standing in for one.

This article reports on active, unresolved litigation (allegations, not proven findings), a currently pending California rulemaking that may still change before finalization, and federal and state regulations as codified at publication. Sources: ClassAction.org, AboutLawsuits.com, PubMed, SAGE Journals, American Cancer Society / IARC, ChemLinked, FDA, Congressional Research Service, Safe Cosmetics / Campaign for Safe Cosmetics, NCBI / IARC Monographs, New York DEC, California DTSC, and PubMed / Darbre et al. 2004. This is not medical advice.