Does Mouthwash Expire?
To understand expiration dates on mouthwashes, you first need to know that the FDA and the American Dental Association (ADA) divide mouthwash into two categories: therapeutic and cosmetic.
Cosmetic Mouthwash: This type of mouthwash can help mask bad breath. But it's not going to correct dental concerns, such as gum disease, enamel wear, tooth decay, plaque buildup, or dry mouth. If you're looking for a mouthwash that helps control or correct specific problems, you'll want a therapeutic mouthwash.
Although the FDA doesn't control cosmetic mouthwashes, you'll still want to be cautious about their expiration dates. It's likely a cosmetic mouthwash will decline in quality the longer it sits on your bathroom shelf.
Therapeutic Mouthwash: These mouthwashes contain active ingredients the FDA regulates, such as those listed by the ADA: fluoride, peroxide, essential oils, cetylpyridinium chloride, and chlorhexidine.
If you have an old bottle of therapeutic mouthwash lying around, it's essential to pay attention to its expiration date. If the bottle is past its prime, it's likely the active ingredients have started to lose their effectiveness.
It's too bad you can't give mouthwash the sniff test as with milk to determine if you should throw it out. Just be aware that using therapeutic mouthwash past its expiration day means it won't be able to do the job as well as it could when it was fresh off the shelf.