Listerine has been one of the most recognizable names in oral care for decades. The bold promise splashed across the label, that it kills 99% of germs that cause bad breath, plaque, and gingivitis, has convinced millions to pour a capful into their mouths daily. The minty burn has become synonymous with “clean.” However, new research is shining a light on a serious problem with this marketing claim, and it could change the way you think about mouthwash altogether.

The Lawsuit and the Research Behind It

The makers of Listerine Cool Mint are facing legal challenges for false advertising. At the heart of the lawsuit is a study published in the Journal of Medical Microbiology, which suggests that the product does much more than kill the germs it claims to target. Instead of leaving your mouth cleaner and healthier, the study found that Listerine use increased levels of certain dangerous bacteria compared to a control mouthwash. That’s the opposite of what most people hope when they swish.

The Complexity of the Oral Microbiome

To understand why this happens, it helps to zoom out. Your mouth is home to a vast ecosystem: about 700 different species of bacteria live there. Some of these bacteria are harmful, but many are beneficial and essential to health. They play key roles in protecting against pathogens, supporting healthy gums, and producing molecules like nitric oxide that help regulate cardiovascular function. In a healthy mouth, there’s balance. The “good” bacteria keep the “bad” bacteria in check, and your oral microbiome stays stable.

Listerine disrupts that balance. With its high alcohol content and broad-spectrum antimicrobial approach, it doesn’t discriminate between good and bad microbes. When the product wipes out nearly everything, the result is a temporary clean slate. But nature abhors a vacuum. Harmful bacteria are often faster at repopulating than beneficial ones, which means the balance tips favor the very organisms you were trying to control in the first place.

The Domino Effect of Disrupting Oral Balance

When harmful bacteria dominate the oral microbiome, the consequences ripple far beyond bad breath and plaque. Some of these microbes are linked to gum disease, tooth decay, and inflammation in the mouth. But the impact doesn’t stop there. Research increasingly shows that oral health is deeply connected to overall health. Harmful bacteria from the mouth can enter the bloodstream, contributing to systemic inflammation. Gum disease has been linked to cardiovascular problems, diabetes, and even cognitive decline. By nuking the oral microbiome daily with a product like Listerine, you may unintentionally raise your risk for these broader health challenges.

Why “Kills 99% of Germs” Isn’t Always a Good Thing

The appeal of products that promise to kill germs is easy to understand. It plays into the cultural idea that bacteria are harmful and cleanliness means eliminating them. But the reality is more nuanced. Our bodies are filled with bacteria on the skin, gut, and mouth; most are beneficial or neutral. Health depends on maintaining a balanced ecosystem, not scorched-earth tactics. Listerine’s 99% kill rate sounds impressive on a label, but it’s an oversimplification that ignores how microbial communities work.

The Alcohol Factor

One of the main active components in Listerine is alcohol. While alcohol is effective at killing bacteria, it comes with downsides in an oral environment. It dries out the mouth, reducing saliva flow. Saliva is a natural defense against harmful microbes because it helps wash away food particles and neutralize acids. When the mouth is dry, harmful bacteria gain another advantage. Combined with the disrupted microbiome, this creates a perfect storm for oral health problems over time.

Beyond the Mouth: Systemic Concerns

The oral microbiome doesn’t exist in isolation. What happens in the mouth influences the entire body. Harmful bacteria that overgrow after repeated Listerine use can contribute to chronic inflammation, a driver of many modern health conditions, from heart disease to metabolic disorders. There’s also growing concern that long-term use of alcohol-based mouthwashes may interfere with nitric oxide pathways in the body, a process vital for cardiovascular health and blood pressure regulation. Instead of promoting longevity and well-being, daily swishing with a product like Listerine may be undermining it.

What to Use Instead

The good news is that you don’t have to give up mouthwash entirely to protect your oral health. The key is to choose products that support balance rather than destroy it. Natural, non-toxic alternatives are available that use ingredients like essential oils, xylitol, or mineral-based compounds to freshen breath and support the oral microbiome without wiping out the good bacteria. Some dentists recommend using saltwater rinses as a simple, effective, and safe option. Others suggest rinses formulated with aloe vera or herbal extracts, which can calm inflammation without disrupting microbial diversity.

If you want to take it a step further, you can focus on building oral health from the ground up with habits like tongue scraping, oil pulling with coconut oil, and eating a diet rich in whole foods that nourish both you and your microbiome. These approaches may not give the instant burn of an alcohol-based rinse, but they work with your body.

The Bigger Lesson

Listerine’s false advertising lawsuit is just one example of a larger issue: how marketing often oversimplifies health into quick, dramatic claims that ignore complexity. “Kills 99% of germs” sounds great in a commercial, but it can mean dismantling a delicate ecosystem that your health depends on. The obsession with killing germs at all costs, whether in the mouth, on the skin, or in the home, has fueled the rise of products that may be doing more harm than good. Health is about balance.

Final Thoughts

If you’ve been swishing Listerine every morning, it’s worth reconsidering what that blue liquid does for your health. The minty freshness may feel satisfying, but the disruption it causes to your oral microbiome can have long-term consequences. Instead of leaning on products that promise a quick fix, focus on approaches that respect your body’s natural balance. Real health doesn’t come from killing 99% of germs; it comes from supporting the ecosystems within you that keep you resilient and strong.

References:

1. Laumen JGE, Van Dijck C, Manoharan-Basil SS, de Block T, Abdellati S, Xavier BB, Malhotra-Kumar S, Kenyon C. The effect of daily usage of Listerine Cool Mint mouthwash on the oropharyngeal microbiome: a substudy of the PReGo trial. Journal of Medical Microbiology. 2024;73(6). doi: 10.1099/jmm.0.001830. PMID: 38833520.