Plaintiff Cites Study Claiming Listerine Can Cause Cancer

Listerine touts its Cool Mint mouthwash as having the ability to “kill 99% of germs” that cause common oral ailments.

Daily use of the product, however, has been shown to result in the proliferation of more bacteria associated with several deadly cancers, according to a Milberg class action complaint filed in California federal court.

Anyone who purchased Listerine Cool Mint may be able to join this lawsuit as a class member and recover compensation under consumer protection laws.

Listerine and the Oral Microbiome

Health-conscious consumers have become increasingly aware of the role the gut microbiome—the ecosystem of microorganisms, including bacteria, that live in the digestive tract—plays in overall health, and how diet influences the gut microbiome.

Similarly, the mouth is home to numerous microorganisms that comprise the oral microbiome, which like the gut microbiome is crucial to maintaining health and can be affected by what we eat and the products we use.

The regular use of Listerine mouthwash should be carefully considered.

A 2019 study, for example, notes that the oral microbiome “is crucial to health as it can cause both oral and systemic diseases.”

The study also notes that microbiome research is in its early stages and data is continually being added to this field of study.

One such study, published in 2024 in the Journal of Medical Microbiology, looked at the effect of Listerine Cool Mint mouthwash on the oral microbiome. It found an association between daily Listerine usage and an increased abundance of oral bacteria that has been linked to serious health problems, including periodontal diseases, esophageal and colorectal cancer, and systemic diseases.

The study found higher amounts of the bacteria Fusobacterium nucleatum and Streptococcus anginosus in the oral microbiome of study participants who used Listerine Cool Mint for three months compared to those receiving a placebo.

“These findings suggest that the regular use of Listerine mouthwash should be carefully considered,” the study authors conclude.

Listerine Fails to Warn Consumers About Health Risks

Listerine advises consumers to use the mouthwash twice per day for 30 seconds and to seek medical help if they swallow more than a minimal amount of it.

Unfortunately for them, swallowing Listerine Cool Mint is not the only danger the product poses.

In a 35-page complaint filed in U.S. District Court for the Central District of California, Milberg class action attorneys allege that Listerine Cool Mint is deceptively and misleadingly marketed by manufacturer Johnson & Johnson because it does not warn consumers that regular use of the product can cause the proliferation of harmful bacteria.

The Product, when used regularly and as intended, results in the proliferation of bacteria associated with several dangerous cancers.

If anything, the complaint states, product labeling suggests the opposite with its claim that Listerine has the ability to kill germs, prevent and reduce plaque and gingivitis, and leave the mouth “fresher and cleaner”—claims that a reasonable consumer would interpret as meaning that Listerine eliminates most harmful bacteria in the mouth, when in fact regular use could raise oral levels of disease-causing bacteria.

The general consensus in published scientific literature is that the oral and gastrointestinal microbiomes play a significant role in a variety of cancers that are established, promoted, and protected by imbalances of bacteria.

• Fusobacterium nucleatum is linked to oral cancer, head and neck cancer, colorectal cancer, pancreatic cancer, esophageal cancer, and breast cancer
• Streptococcus anginosus is linked to gastro-intestinal cancer and colorectal cancer.

In addition, both types of bacteria have been found to be predominant in patients suffering from oral squamous cell carcinoma.

National and California Classes Sought

Growing awareness of oral health is driving the expansion of the oral rinse/mouthwash market, which was valued at $6.51 billion in 2021 and is expected to more than double to $15.7 billion by 2032.

More than 60 U.S. companies make mouthwash, and Listerine is the leading brand, racking up around $350 million in annual sales.

For consumers such as plaintiff Paige Vasseur, product labels and warnings are a rich source of information that differentiate one product from another and influence their purchase decisions.

The omission that Listerine causes cancer-causing bacteria to thrive in the mouth is a material fact for any consumer item, and especially for a product like Listerine that promotes health and disease prevention.

Vasseur claims in the complaint that, if not for the omission of this fact, she would not have purchased Cool Mint Listerine—or at a minimum would have paid less for it. She seeks to establish two consumers classes that she says lost the entire benefit of the bargain when they bought the mouthwash:

• All consumers who purchased Cool Mint Listerine anywhere in the United States; and
• All consumers who purchased Cool Mint Listerine in the State of California.

Her lawsuit cites violations of California’s Unfair Competition Law, False Advertising Law, and Consumer Legal Remedies Act. Vasseur is represented by Milberg’s Trenton Kashima, Alex Straus, and Nick Suciu III.

Milberg pioneered the use of federal class action litigation and remains a national leader in filing class action lawsuits. From 2021 to 2023, Milberg filed the third most consumer protection lawsuits of any firm in the country. Over the same period, the firm filed the fifth most class action lawsuits.