Unilever Hair Loss Lawsuits Face Off Against Cosmetic Science

Well, well, well... if it isn't another class action built on claims that science keeps undercutting.

Last week, plaintiffs filed a product liability lawsuit in New Jersey federal court against Unilever's Conopco division, alleging TRESemmé hair products caused hair loss due to the presence of preservative DMDM hydantoin (“DMDM”).

Why it matters: For beauty brands, navigating the gap between consumer perception, legal vulnerability, and scientific consensus is an ongoing challenge. This case highlights how established, regulatory-approved ingredients can still trigger costly litigation, even when scientific evidence supports their safety.

Dose Makes the Poison

DMDM has been used globally for decades as a preservative valued for its antimicrobial properties, which means formulators only need tiny amounts for it to be effective.

DMDM works by slowly releasing trace amounts of formaldehyde throughout a product’s shelf life, preventing microbial growth and preserving the formula.

DMDM should not be confused with formaldehyde used in professional hair-straightening treatments, where high concentrations are applied directly to the hair and release a hazardous gas when heated. According to a 2011 warning letter to hair-straightening brand Brazilian Blowout, after analyzing 50 mg samples of the product, the Food and Drug Administration (FDA) reported finding methylene glycol (the liquid form of formaldehyde) at concentrations ranging from 8.7% to 10.4%.

By comparison, DMDM is typically used in shampoos at a concentration of 0.0005% to 0.6%. The European Union also permits its use at concentrations up to 0.6%.

Irritation vs. Hair Loss

Can DMDM cause scalp irritation? Yes, though rarely, absent a formaldehyde allergy. That's the opening plaintiffs exploit: irritation and allergic dermatitis can sometimes contribute to temporary shedding.

But a 2023 risk assessment published in the International Journal of Toxicology evaluated shampoos containing DMDM at the maximum permitted concentration. The researchers concluded that at these levels, DMDM is “not expected to increase the risk of skin sensitization induction in healthy individuals not previously sensitized to formaldehyde.”

That conclusion is consistent with cosmetic safety regulators. The Cosmetic Ingredient Review Expert Panel has repeatedly concluded that DMDM “can be used safely in cosmetics, if established safety limits are not exceeded," and both US and European regulators continue to permit its use within established concentration limits.

Hair loss can be triggered by anything from genetics, hormonal changes, and nutritional deficiencies to stress and medications. As consumers increasingly seek targeted solutions for thinning, new players are entering the market, such as when a former GQ editor and Google alum launched hair longevity brand Manuscript to address these complex concerns. However, proving that a single cosmetic ingredient is the sole culprit remains a high legal hurdle.

This demand for ingredient safety is also reshaping other categories, as seen in how millennial parents drive a premium boom in kids’ personal care by prioritizing transparency and clean formulations.

“If they [the plaintiffs] are going after TRESemmé because they think DMDM made their hair fall out, they'll have a tough time winning the case,” said Perry Romanowski, cosmetic chemist and educator, who previously formulated products for brands including TRESemmé and St. Ives.

Romanowski told BeautyMatter that while the allergy allegation is scientifically plausible, the claim that DMDM hydantoin routinely or directly causes hair loss is poorly supported. “Unless these plaintiffs have substantially better medical and expert evidence than what appears in the complaint, I’d consider their likelihood of ultimately prevailing fairly low.”

Serial Defendant

Unilever's personal care division has faced enough DMDM suits to keep its counsel busy. The cases, however, have produced a mixed bag of results.

The company settled a 2012 lawsuit for more than $10 million after consumers reported hair loss and scalp burns from a recalled Suave Professionals smoothing kit.

A 2022 suit alleging an unsafe, undisclosed TRESemmé ingredient was dismissed for insufficient evidence. And a 2023 case was dismissed with prejudice this March after the plaintiff's expert, under deposition, admitted his opinion was wrong and that he "could not even speculate" how TRESemmé caused the alleged harm.

Follow the Money

Class actions serve an important purpose by holding companies accountable. But in many product liability settlements, consumers receive little more than refunds, while attorneys collect millions in fees. This type of litigation is big business for attorneys looking for a quick settlement.

The US is one of the most litigious countries globally, and class-action lawsuits have become a big issue for brands of all sizes, potentially crippling if not fatal for small to midsize brands.

A plaintiff’s attorney just needs one allegation to get the litigation going.

This suit's survival will hinge less on its allegations than on proving causation. Despite a substantial body of scientific research concluding that DMDM is safe when used at approved concentrations and that, according to Romanowski, the TRESemmé shampoo had a concentration of .2%, these lawsuits will most likely continue.