Listerine users are suing the mouthwash’s maker, Johnson and Johnson, for claiming it puts them at risk of cancer.
A previous study found that the company’s Cool Mint flavored mouthwash increased levels of oral bacteria linked to throat and colon cancer.
Now, a class-action lawsuit has been filed in California accusing J&J of failing to disclose the alleged risks to customers.
The $5 mouthwash instructs consumers to use it for 30 seconds twice a day to kill 99.9 percent of all bacteria in the mouth.
But research suggests that daily use causes levels of two species of bacteria to increase: Fusobacterium nucleatum and Streptococcus anginosus.
These have been linked to cancer in the esophagus (the tube that connects the throat and stomach) and colon.
The researchers also observed a decrease in a group of bacteria called actinobacteria, which may protect against cancer by helping to reduce inflammation.
Dr. Karen Saghiyan, a colon cancer researcher at Cedars Sinai Medical Center in Los Angeles, drew attention to the lawsuit in an online post that has racked up more than 800,000 views.
Using Listerine Cool Mint mouthwash every day could increase the risk of developing esophageal and colorectal cancer, according to a new scientific study (file image)
He described the studies as “extremely interesting” but also said it was worrying that Listerine could cause an increase in Fusobacterium species.
The lawsuit was filed by Paige Vasseur, who is seeking damages and accusing Listerine of deceptive marketing.
He bought the mouthwash regularly from 2019 to February 2024, but says he wouldn’t have done so if he had been aware of the risks.
Vasseur says the brand should carry a warning on its bottles about cancer and is seeking compensation for the costs of purchasing the product.
She is asking others to apply to join the lawsuit.
Cancers are increasing in younger age groups, including colon and throat cancers.
Colon cancer diagnoses among people under age 50, which are classified as early-onset, are expected to increase by 90 percent in people ages 20 to 34 between 2010 and 2030.
Doctors are struggling to find the cause of the rise in colon cancers, blaming everything from obesity to food additives to alterations in the gut microbiome. The increase in throat cancers has been linked to HPV infection or a sexually transmitted disease infection.
Johnson and Johnson, which makes Listerine mouthwash, has not yet responded to the class action lawsuit.
The 35-page class action lawsuit was filed in early September in the United States District Court for the Central District of California.
Scientists at the Institute of Tropical Medicine in Antwerp, Belgium, found that two species of bacteria were more prevalent after three months of daily mouthwash use (file image)
Data from JAMA Surgery showed that colon cancer is expected to increase by 90 percent in people ages 20 to 34 by 2030.
J&J has previously said there is still “no evidence” that its product causes cancer.
However, a study by researchers in Belgium, investigating the impact of mouthwash use on 59 gay men, suggested there could be a link. Initially they were investigating how it affected the risk of STIs.
Participants used Listerine mouthwash for three months and then a placebo mouthwash for the next three.
In another study from June of this year, researchers said they could be one step closer to solving the mystery of the cause of rising colon cancer in young people.
They said that eating too much sugar and little fiber causes the intestine to be colonized by bacteria that “accelerate the aging” of cells. These were the Fusobacteria.
In another paper from March this year, they found that half of all colon cancer tumors contain Fusobacterium, suggesting a link.
Dr Saghiyan said on TikTok: ‘Earlier this year, I read about… fusobacterium species in the oral cavity associated with an increase in tumors in people with colorectal cancer.
“I found it extremely interesting because fuso bacteria is actually an oral bacteria, and why would it be inside someone’s colon?”