The Mouthwash That May Feed Cancer

EvilCorporations.com • Case 2:24-cv-07487, U.S. District Court, Central District of California • 43 min read

For years, millions of Americans have stood at their bathroom sinks twice a day, swishing Listerine Cool Mint on the instruction of a company that told them they were “killing 99% of germs.” A federal class action lawsuit filed September 3, 2024 says that claim is a lie, and the real story is significantly more disturbing: the product may be feeding the very bacteria linked to some of the most deadly cancers humans face.

What It Actually Costs to Be Deceived at the Bathroom Sink

There is a specific kind of violation that happens when a corporation turns your health routine against you.

Think about what Listerine represents to the people who use it. It is a product you use twice a day, every day, inside your own mouth. You do not use it once at a party or occasionally on a weekend. You use it with your kids in the bathroom before school. You use it before a job interview. You use it when you are sick and trying to feel better. You use it specifically because the company told you it was the healthy choice, the responsible choice, the choice that would make your mouth cleaner and your body safer.

Plaintiff Paige Vasseur bought and used Listerine Cool Mint from approximately 2019 through at least February 2024. That is five years of twice-daily use, following the company’s instructions exactly, trusting the label she read before she bought it. The product told her it was killing 99% of germs. She had no reason to believe that the same product was simultaneously doing the opposite for two types of bacteria that researchers have connected to oral cancer, colorectal cancer, pancreatic cancer, esophageal cancer, breast cancer, and cancers of the head and neck.

She is one person. The class action includes thousands of consumers across the United States. These are people who believed in the product. Many of them are health-conscious, exactly the audience J&J’s own marketing targeted. They chose mouthwash because they were trying to be careful about their bodies. The lawsuit says that care was weaponized against them.

The betrayal is not abstract. F. nucleatum, one of the bacteria the lawsuit says Listerine causes to proliferate, has been shown to survive the journey from the mouth through the digestive tract. It thrives under acidic gut conditions. Research cited in the complaint links its oral concentration to the prognosis of colon cancer. That means the bacteria multiplying in your mouth from a product you gargle with every morning may be traveling deeper into your body over months and years of use.

Nobody warned these people. The warning label on the bottle told them not to let children under 12 use it, and not to swallow too much. The company was explicit and precise about the dangers it chose to disclose. The danger it did not disclose was the one it had the most reason to know about, given that the complaint alleges J&J conducted more than 50 clinical trials on this product, at least 30 of which lasted six months or longer. Five years of testing across more than 3,000 subjects. The company touted those numbers in its own marketing. What they did not say was what those studies may have shown about bacterial proliferation.

The science underlying this lawsuit was published in June 2024. Federal law required J&J and Kenvue to update their label with safety information as soon as there was reasonable evidence of a serious hazard. The lawsuit was filed in September 2024. At the time of filing, the complaint states the warning had still not been added. The product was still on shelves, still carrying the “kills 99% of germs” claim, still being recommended for twice-daily use.

That is the non-financial ledger: five or more years of a morning and evening ritual that may have been harming the people who most trusted it. A company that had every tool and every regulatory obligation to warn them. And a choice, documented in this lawsuit, to keep selling instead.

Straight From the Complaint: What They Said, What They Hid

The following passages come directly from the filed complaint (Case 2:24-cv-07487). Nothing is paraphrased. These are the documents.

“Defendants market and label the Product as having the ability to ‘kill 99% of germs that cause bad breath, plaque & gingivitis’ and providing ‘a fresher and cleaner mouth than brushing alone.'”

• This is the central claim on the product’s packaging. The complaint argues that by promising to kill 99% of germs broadly, the company implied it was killing harmful bacteria, including those now known to be linked to cancer. The reality documented by research is the opposite.
• The phrase “germs” is a broad category that includes bacteria. A consumer reading the label would reasonably conclude harmful bacteria were being eliminated, not multiplied.

“A recent study found that after three months of normal use, Listerine Cool Mint greatly affected the microbiome composition. Specifically, after the three-month period, F. nucleatum and S. anginosus were found to be significantly more abundant than at the measured baseline of patients.”

• This references the peer-reviewed PReGo trial substudy, published June 2024 in the National Library of Medicine. The finding is direct: the product increases two cancer-linked bacteria after three months of normal, directed use.
• “Significantly more abundant than at the measured baseline” means these bacteria grew beyond starting levels, not just that they survived. The product did not maintain the mouth’s bacterial balance; it altered it in a documented harmful direction.

“Defendants tout the extensive clinical testing of the Product. Not only for its effectiveness, but also for its safety. In particular, Defendants claim that ‘Listerine antiseptic is the most extensively tested OTC mouthwash’ and that it had been ‘examined in more than 50 clinical trials more than 30 of which lasted 6 months or longer.’ Defendants further tout the ‘proven safety and tolerability of Listerine in clinical studies’ and represent that ‘as powerful as LISTERINE is, its safety is supported by fifteen 6-month studies conducted over a 20 year period in 3203 subjects.'”

• This is the company’s own marketing language, quoted from the Listerine Professional Canada website. It proves that J&J and Kenvue held themselves out as the most safety-tested mouthwash on the market, with over 50 trials and 3,203 subjects.
• The complaint argues this extensive testing program means the company either found or should have found evidence of bacterial proliferation long before the June 2024 study became public. Claiming deep clinical expertise while omitting known risks is the core of the fraudulent concealment claim.
• Federal regulation 21 CFR § 314.80(b) places post-marketing surveillance responsibility on the manufacturer. With 50-plus trials already run, the company cannot credibly claim ignorance.

“Defendants’ omission also violates 21 CFR § 201.80(e), which requires a manufacturer to revise its label ‘to include a warning as soon as there is reasonable evidence of an association of a serious hazard with a drug’, § 314.80(b) which places the responsibility for post-marketing surveillance on the manufacturer, and 73 Fed. Reg. 49605 which mandates that ‘manufacturers continue to have a responsibility under Federal law … to maintain their labeling and update the labeling with new safety information.'”

• This passage establishes that the failure to warn is not just a moral failing; it is a documented violation of specific federal regulations. The standard is “reasonable evidence,” not certainty. A peer-reviewed study published in the National Library of Medicine meeting this threshold.
• By the time of the complaint’s filing in September 2024, at least three months had passed since the June 2024 publication. Federal law required a label update. The complaint states none had been made.

“Defendants’ concealment was material and intentional because people are concerned with the health effects of products that they are putting onto and into their bodies. Indeed, consumers that use the Product do so to prevent oral disease and kill harmful bacteria, not to increase such harmful bacteria’s prevalence in their mouth.”

• The word “intentional” is carrying serious legal weight here. The complaint argues J&J and Kenvue did not accidentally omit this information. They made a choice, knowing that disclosure would eliminate consumer demand for the product.
• Paragraph 147 of the complaint states directly: “Defendants know that if they had not omitted that the Product caused the proliferation of cancer-causing bacteria, then Plaintiff and the Class would not have purchased the Product at all or paid a premium for it; however, Defendants wanted to increase sales and profits.”

The Two Bacteria: What They Do and Where They Travel

The lawsuit centers on two specific bacterial species. Understanding what they are and how they connect to cancer is essential to understanding why this case matters.

• Fusobacterium nucleatum (F. nucleatum) is a naturally occurring oral bacterium that researchers have linked to oral cancer, head and neck cancer, colorectal cancer, pancreatic cancer, esophageal cancer, and breast cancer. The National Cancer Institute has published on its connection to colorectal cancer specifically. Research cited in the complaint shows F. nucleatum promotes colorectal cancer metastasis, influences the tumor microenvironment, and worsens cancer prognosis. Its concentration in the mouth has been used to predict colon cancer outcomes.
• Streptococcus anginosus (S. anginosus) has been linked to gastrointestinal cancer and, in cases, colorectal cancer. Research published in Science Direct found it promotes gastric inflammation, atrophy, and tumorigenesis in mice. Both S. anginosus and F. nucleatum were found to be the predominant bacteria in patients with oral squamous cell carcinoma in a 2023 salivary microbiome study.
• Both bacteria are capable of traveling from the mouth through the digestive tract. F. nucleatum specifically has been shown to survive under acidic gut conditions, the kind found in the stomach and colon, which suggests a mechanism by which oral bacterial changes can contribute to gut cancers.
• The PReGo trial substudy, published in the National Library of Medicine in June 2024, measured participants’ oral microbiomes at baseline and again after three months of daily Listerine Cool Mint use. Both F. nucleatum and S. anginosus were “significantly more abundant” after three months compared to baseline. This was not a fringe publication; it appeared in a peer-reviewed medical database operated by the National Institutes of Health.

Who Gets Hurt and How Bad It Gets

Public Health

The documented bacterial effects of Listerine Cool Mint connect directly to some of the most lethal and common cancers affecting Americans.

• F. nucleatum has been linked in peer-reviewed research to oral cancer, head and neck cancer, colorectal cancer, pancreatic cancer, esophageal cancer, and breast cancer. These are cancers with high mortality rates, limited early detection tools, and expensive, grueling treatment paths.
• Colorectal cancer is the second-leading cause of cancer death in the United States. The complaint documents that F. nucleatum has been implicated in every stage of colon cancer development, including promotion, metastasis, and worsening of prognosis. Its oral abundance has been used to predict cancer staging in patients already diagnosed.
• Pancreatic cancer carries a five-year survival rate of approximately 12% across all stages. If F. nucleatum plays a documented role in its development, then a product encouraging this bacteria’s growth in the mouth of healthy people carries a public health risk that cannot be dismissed as speculative.
• The complaint describes “oral dysbiosis,” a disruption of the balance of bacteria in the mouth, as having “downstream effects that are both understood and currently being studied.” This means the known harms are a floor, not a ceiling; the full scope of the damage may not yet be quantified.
• Listerine directs consumers to use the product twice daily. This is not occasional or incidental exposure. It is a structured, repeated biological intervention, twice a day, every day, inside the human body. The accumulation of that exposure over months and years, given what the PReGo study found at three months, is a public health question the company has declined to answer on its label.
• Consumers lack any ability to independently test a product’s effect on their microbiome at the point of sale. The complaint is explicit: this is a risk that only the manufacturer could evaluate, disclose, and warn against. The failure to do so is not a gap in consumer responsibility; it is a corporate choice.

Economic Inequality

The financial injury in this case compounds along familiar lines: the people least able to absorb the cost of cancer are the same people most likely to rely on over-the-counter products marketed as health tools.

• Listerine Cool Mint is a mass-market consumer product available at every grocery store, pharmacy, and big-box retailer in the country. It is not a luxury item. Its user base is broad, encompassing working-class and middle-income households who trust OTC product labeling as a substitute for expensive medical consultations about daily hygiene products.
• The mouthwash market was valued at $6.51 billion in 2021 and is projected to reach $15.7 billion by 2032. J&J and Kenvue profit from a market driven by health-conscious consumers who are specifically motivated by germ-killing claims. Those consumers are paying a premium for a product whose primary selling point, the “kills 99% of germs” label, the lawsuit alleges is actively misleading.
• The class action seeks damages exceeding $5 million at minimum. The actual class includes thousands of consumers across all 50 states, each of whom paid for a product they allege had no safe, merchantable value. The economic harm scales across every individual purchase price, multiplied by years of repurchase across the class period.
• If any class members develop cancers linked to F. nucleatum or S. anginosus, the financial consequences extend far beyond a refund for mouthwash. Cancer treatment in the United States averages tens of thousands of dollars per year. Medical bankruptcy is a documented outcome for cancer patients. The lawsuit does not pursue this downstream financial injury directly, but the connection between the product, the bacteria, and the cost of cancer is embedded in the complaint’s core allegations.
• The complaint notes that Defendants “wanted to increase sales and profits” as the motivation for the concealment. The structure is straightforward: the company protected revenue by withholding safety information that would have eliminated consumer demand. The consumers absorbed the risk. The corporation kept the money.

The Number That Defines the Trade

Who Is Responsible and What You Can Do

The defendants named in this lawsuit are corporate entities, and accountability runs through both of them: Johnson & Johnson Consumer, Inc. (principal place of business: 199 Grandview Rd, Skillman, NJ), which manufactured and distributed the product until February 2022, and Kenvue Inc. (principal place of business: 199 Grandview Rd., Skillman, NJ), the spinoff corporation that has owned and sold the product since then. The complaint was filed by lead plaintiff Paige Vasseur on behalf of a nationwide class.

Regulatory Watchlist

• U.S. Food and Drug Administration (FDA): Listerine Cool Mint is classified as an OTC drug regulated under the Federal Food, Drug, and Cosmetics Act. The FDA has authority to require label updates, declare products misbranded, and pull products from commerce. 21 CFR § 201.80(e) already mandates a warning update. The FDA has not yet acted publicly on this product as of the complaint’s filing date.
• Federal Trade Commission (FTC): The “kills 99% of germs” claim is consumer-facing advertising. If it is materially misleading as the complaint alleges, the FTC has jurisdiction over deceptive advertising practices in consumer products.
• U.S. Department of Justice (DOJ): The complaint references potential violations of the Federal Food, Drug, and Cosmetics Act, 21 U.S.C. § 301 et seq. Federal criminal and civil enforcement of FDCA violations falls within DOJ jurisdiction.
• California Attorney General / State AG Offices: The complaint invokes California’s Unfair Competition Law, False Advertising Law, and Consumer Legal Remedies Act. State-level attorneys general in California and other states have independent authority to investigate and act on consumer protection violations of this scale.

What You Can Do Right Now

• If you have purchased Listerine Cool Mint and used it regularly, document your purchase history. Receipts, loyalty card records, and subscription delivery records are all potentially relevant. The class period covers all U.S. purchases during the applicable statute of limitations.
• Contact class action counsel directly. The law firms involved are Milberg Coleman Bryson Phillips Grossman PLLC (San Diego, CA; tkashima@milberg.com; tel 619-810-7047) and Shub & Johns LLC (Conshohocken, PA; jshub@shublawyers.com; tel 610-477-8380). Both are listed as counsel for the plaintiff class.
• Tell your community, specifically friends and family who use mouthwash daily. The harm alleged here accumulates over months and years. People who have been using this product for years without knowing the bacterial risk cannot act on information they have never been given.
• File a complaint with the FDA’s MedWatch safety reporting program (fda.gov/safety/medwatch). Consumer reports create a documented public record that regulators use to evaluate the scale of a product safety concern.
• Connect with mutual aid health networks and consumer protection organizations in your area. Consumer rights groups and community health advocates have resources for people navigating product safety concerns, especially those without access to private legal counsel.
• If you are a healthcare provider, be aware that F. nucleatum and S. anginosus proliferation from mouthwash use may be a factor in your patients’ oral microbiome assessments. Share this litigation with professional networks where appropriate.