Does Dental Floss Expire? Why It Might Matter

If you’ve ever been cleaning out the back of a bathroom shelf or drawer and found a pack of dental floss that looks like it dates back to the last century, you’ve probably asked yourself the same question that people around the world have wondered at one point or another: can dental floss really expire?

On one hand, the good news is that the answer is pretty much no, dental floss cannot expire! On the other hand, depending on how long that spool of minty-fresh thread has been sitting around, it may have become flavorless and brittle.

When Might Expired Dental Floss Be Harmful?

Unlike other common dental supplies like toothpaste and mouthwash, dental floss that’s been sitting around for a while is not going to be actively dangerous. Because the other two products mentioned above contain alcohols, preservatives, and other potentially perishable ingredients, they should be disposed of as soon as they pass their “best by” date.

In contrast, dental floss doesn’t really have any ingredients that could go bad. Instead, the only real concern with using old dental floss is that it may be slightly more prone to brittleness or fraying.

Neither of these conditions are particularly harmful in and of themselves, but they can make flossing difficult or even uncomfortable, depending on the health of your gums. Frayed dental floss can drag against the gums and potentially irritate the skin, which may not feel comfortable upon repeated uses of the floss.

Brittle floss, on the other hand, is far more likely to result in active discomfort, as a splinter of floss can get stuck between two teeth or in the gums. If this is the case, it may be difficult to remove and just generally aggravating to have to handle.

Why Does Dental Floss Have an Expiration Date, Anyway?

If you’re looking at a container of dental floss right now, you may be noticing that, despite this article’s assurances as to its eternal shelf-life, your dental floss still has an expiration date.

The reason for this is simple—while the floss itself cannot expire, the waxy coating that is often applied to most commercial flosses can. The wax coating on dental floss is designed to be biodegradable in case any of it rubs off on the teeth and is accidentally swallowed.

Again, it is only the outer coating of the dental floss that can “expire”. Even in this case, the word should be used only loosely, as there is nothing in the wax that can really expire in the traditional sense and cause the health issues that typically go hand in hand with that phrase.

Basically, while neither the wax nor the floss can truly expire in the same way that food and drink can do, the wax coating on most brands of dental floss may begin to break down over time. While this will not hurt the safety of the floss itself, it may lead to other side effects that will have you asking questions like—

Why Does My Dental Floss Taste Funny?

The aforementioned wax coating on dental is really only added for flavor. Research has shown that there’s no real benefit to brushing with waxed floss instead of unwaxed, but a lot of people prefer that minty-fresh feeling that flavored flosses leave behind.

Unfortunately, because the flavoring is usually packed into the same waxy coating that starts to break down over time, “expired” dental floss may have a weaker or even a nonexistent flavor. While unflavored dental floss probably wouldn’t register as a cause for alarm, during the degradation process, you may find that your floss tastes odd.

Again, the compounds used to flavor dental floss are designed to be safe for consumption. Even if your floss is starting to taste a little bit strange, you’re not in any real danger of using a “spoiled” container of floss.

However, if you find that the flavor of your floss is too off-putting—or if you simply miss the more concentrated flavor of a fresh pack of dental floss—there’s absolutely nothing wrong with declaring your floss expired and purchasing a new pack!

In Conclusion

Ultimately, whether you use that expired canister of dental floss or not is entirely up to you. For the most part, you are not going to be in danger of using a “spoiled” product with all of the associated risks that that implies.

However, if you use a long-expired box of dental floss, be aware of the fact that it may not work as well as a brand-new container. While the side effects may range from something as simple as weaker flavor to more frustrating issues like easily breakable thread, the risk vs. reward breakdown is your decision!