Listerine users are suing the mouthwash’s manufacturer Johnson and Johnson over claims it put them at risk of cancer.
A previous study found the company’s Cool Mint flavor mouthwash increased levels of mouth 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 tells consumers to use it for 30 seconds twice a day to kill 99.9 percent of all the bacteria in their mouth.
But research suggests daily uses causes levels of two species of bacterium — Fusobacterium nucleatum and Streptococcus anginosus — to rise.
These have been linked to cancer in the esophagus — the tube that connects the throat and the stomach — and in the colon.
Researchers also saw 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 the Cedars Sinai Medical Center in Los Angeles, drew attention to the lawsuit in a post online that has been viewed nearly 800,000 times.
Using Listerine Cool Mint mouthwash every day could increase the risk of developing esophageal and colorectal cancer, a new scientific study has found (stock image)
She described the studies as ‘extremely interesting’ but also said it was worrying that Listerine could cause a surge in Fusobacterium species.
The new lawsuit was filed by Paige Vasseur, who is seeking damages and accuses Listerine of misleading marketing.
She has purchased the mouthwash regularly from 2019 to February 2024, but says she would not have done so if she was aware of the risks.
Ms Vasseur says the brand should carry a warning on its bottles about cancer, and is seeking damages for the expense of purchasing the product.
She is calling on others to apply to join the lawsuit.
Cancers are surging in younger age groups, including of the colon and throat.
Diagnoses of colon cancer among people under 50 years old, which are classified as early-onset, are expected to rise by 90 percent in people 20 to 34 years old from 2010 to 2030.
Doctors studying the cause of the surge in colon cancers say obesity, additives in food and disruptions to the gut microbiome are likely playing a role.
The uptick in throat cancers has been linked to HPV infection, a common STD.
The 35-page class action was filed in early September in California’s United States District Court for the Central District of California.
Scientists from the Institute of Tropical Medicine in Antwerp, Belgium, found that two species of bacteria were more prevalent after three months of daily mouthwash use (stock image)
Data from JAMA Surgery showed colon cancer is expected to rise 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 but is yet to respond to the latest legal filing.
However, a study by researchers in Belgium found, who were investigating the impact of mouthwash use on 59 gay men, suggested there may be a link.
The participants used the Listerine mouthwash for three months, and then a placebo mouthwash for the next three.
In another study from June this year, researchers said they may be a step closer to cracking the mystery of the cause of rising colon cancers in young people.
They said that eating too much sugar and not enough fiber causes the gut to be colonized by a bacteria that ‘speeds up the aging’ of cells. This was Fusobacteria.
In another paper from March this year, they found that half of all colon cancer tumors contain Fusobacterium.
Dr Saghiyan said on TikTok: ‘Earlier this year, I read about… fusobacterium species in the oral cavity being associated in increase in tumors of individuals with colorectal cancer.
‘I found it to be extremely interesting because fuso bacterium is really an oral bacteria, and why in the world would it be inside somebody’s colon?’
A spokeswoman for Kenvue, formerly part of Johnson and Johnson, said: ‘Studies on the impact of Listerine on oral health have been published in hundreds of peer-reviewed publications for more than a century, making it one of the most extensively tested mouthwash brands in the world.
‘We continuously evaluate the latest science and monitor safety signals to evaluate the benefit risk profile of our products.’
She added: ‘Listerine is safe when used as directed on the label, and there is no evidence that Listerine causes cancer.’
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