You find a bottle of mouthwash in the back of the bathroom cabinet, half-used and long forgotten. Does mouthwash go bad?
The short answer: It depends on what kind you have. Cosmetic mouthwash, the kind that just freshens breath with no other claims, isn’t required to carry an FDA expiration date and holds up for a long time. Therapeutic mouthwash, the kind that claims to fight plaque, gingivitis, or cavities, contains active ingredients the FDA actually regulates as an over-the-counter drug, and those bottles do carry a real expiration date, commonly 2 to 3 years from manufacture. Colgate’s own guidance confirms this timeline and the distinction between the two categories.
Key Takeaways
Therapeutic mouthwash (fluoride, essential oils, CPC, chlorhexidine): Genuinely regulated by the FDA as an over-the-counter drug, with a real expiration date based on stability testing of its active ingredients, commonly 2 to 3 years.
Cosmetic mouthwash (breath-freshening only, no therapeutic claims): Not required to carry an FDA expiration date, but still declines in quality over time.
Past its date, mouthwash usually isn’t dangerous, just less effective. The active ingredients that fight plaque and bacteria gradually break down, so an old bottle mostly just stops doing its job as well.
Contamination is rare but real. The FDA has documented cases of bacterial contamination in oral rinse products, which is part of why manufacturers set and test expiration dates rather than leaving shelf life open-ended.
Alcohol-based mouthwash tends to hold up longer than alcohol-free versions, since the alcohol itself acts as a mild preservative.
Listerine’s own FAQ recommends checking the printed expiration date and replacing the product once it’s passed, rather than judging it by smell or appearance alone.
Why Some Mouthwash Has a Real Expiration Date and Some Doesn’t
Cosmetic vs. Therapeutic Is the Whole Story Here
The FDA and the American Dental Association split mouthwash into two categories, and which one you’re holding determines almost everything about how seriously to take the date on the label. A cosmetic mouthwash only freshens breath and leaves a pleasant taste; it doesn’t claim to treat or prevent anything, which means it’s regulated more like a cosmetic product than a drug and isn’t required to carry an FDA-mandated expiration date.
A therapeutic mouthwash is different. If the label claims it fights gingivitis, reduces plaque, prevents cavities, or kills bacteria, it contains active ingredients like fluoride, cetylpyridinium chloride, essential oils, hydrogen peroxide, or chlorhexidine, and the FDA regulates it as an over-the-counter drug. That means the manufacturer has actually run stability testing to determine how long those specific active ingredients remain effective, and the expiration date on the bottle reflects real data, not just a generic guess.
How Long Mouthwash Actually Lasts
Type
Shelf Life
Therapeutic mouthwash, unop
