OK, TMI: What Does It Mean If Your Floss Is Stinky?

Flossing is a non-negotiable part of our dental hygiene routines to remove plaque and food particles in the places our toothbrushes can’t reach. But if you’ve noticed that when you often use floss, it smells like whatever it’s collected from between your teeth (or worse), you might wonder what it means—and why your floss is stinky.

As it turns out, there are several reasons for bad-smelling floss, some of which may require a visit to your dentist. To find out what is causing the foul odor and how to get rid of the smell when flossing, we talked to board-certified dentists Fatima Khan, DMD, and Rhonda Kalasho Zoumalan, DDS.

5 potential reasons for bad-smelling floss

1. There’s food trapped between your teeth

Foods like steak, chicken, and pork will likely remain stuck between your teeth, and it’s imperative to remove any leftovers right away. “If not removed promptly, it will cause the worst foul odor,” says Dr. Khan. Other foods can lead to stinky floss, too. For instance, residue from sticky foods like candy and dried fruit can linger long after they’ve been consumed and require special attention to make sure they’re completely removed from the surfaces and between spaces of the teeth. She also says that left-behind popcorn hulls can also lead to irritation and gum inflammation and, in turn, bad-smelling floss and bad breath.

Keep in mind that you don’t want any type of food left in your teeth for too long (even those foods that are good for your teeth). “If any food particle sits in your mouth long term, it will cause a foul odor and increase the risk for gum issues and tooth decay,” says Dr. Khan, adding that people with large spaces between their teeth are more susceptible to having these lingering food particles—which is why it’s important to floss correctly and regularly.

2. A broken filling

“If your filling is fractured due to recurrent decay or trauma, it can harbor bacteria,” says Dr. Khan. “When you floss, you may notice the filling pulling up or getting stuck and particles and foul odor being present on the floss.” With this in mind, she says that it’s important to pay a visit to a dentist to have the restoration or filling fixed immediately.

3. Tooth decay

Tooth decay is also a common stinky floss culprit. “If you have tooth decay, especially between your teeth, your floss will smell when flossing at that site,” says Dr. Khan. “When you have dental decay, especially a large cavity—which is a hole in your tooth—bacteria and food particles can get trapped there and lead to bad breath and foul floss odor.” Dr. Khan mentions that if your floss not only has a foul smell but also gets stuck when flossing between your teeth, it might indicate possible tooth decay—and it’s important that you pay a visit to a dentist immediately.

4. Gum disease

“When you have persistent plaque that is sitting on your teeth, it can lead to gum irritation, inflammation, and bleeding,” says Dr. Khan, adding that “when you floss, you might notice bleeding and odor.” She also says that people who are stressed, pregnant, or undergoing hormonal fluctuations can have tender gums that bleed more readily or be caused by improper brushing or flossing, prescription anticoagulants, or deficiencies in vitamins C or K. In any case, she says it’s important to talk to a dentist to figure out how to alleviate bleeding gums to prevent foul-smelling floss and breath.

5. Halitosis

“If you have halitosis and your breath smells, so will your floss,” says Dr. Khan. People with halitosis may also notice a sticky build-up on their teeth, in addition to a foul odor, making them more prone to anaerobic bacteria, which produces malodorous volatile sulfur compounds. She adds that a decrease in saliva flow can lead to an overgrowth of this bacteria, which can be further exacerbated by mouth breathing.

Is bad-smelling floss linked to bad breath?

“Bad-smelling floss is almost always a good indicator that you have bad breath,” says Dr. Khan. She adds that you can also determine whether you have bad breath or not through a number of other ways, like using a tongue scraper or wiping a gauze on your tongue—and then smelling it. “A white coating on your tongue [or] a bad taste in your mouth are also signs that you have bad breath,” she says.

What causes bad breath?

There are a number of common bad breath culprits, including certain foods and beverages, like garlic, onions, fish, alcohol, and coffee, says Dr. Khan. She mentions that many of the same reasons for stinky floss are behind bad breath, too. “If you have food trapped in your teeth, if you have gum disease, if you have cavities or broken restorations [trapping] bacteria and food particles—all lead to bad breath,” she says, adding that increased production of odor-causing volatile sulfur compounds in the mouth and throat (which are closely linked to halitosis¹), as well as a decrease in saliva, can lead to unwanted mouth odors.

How to prevent unwanted mouth odors

If you catch a funky whiff after flossing, Dr. Kalasho recommends paying a visit to your dentist, who can help you determine the root cause of the odor and provide an appropriate solution to tackle the problem. Additionally, you may want to follow her tips to prevent unwanted mouth odors—and get rid of the smell when flossing:

1. Visit your dentist regularly

There are dental oral hygiene practices to follow to prevent bacteria from accumulating in your mouth. The first—and most important—one is to visit your dentist regularly. Typically, Dr. Kalasho recommends visiting your dentist every three to four months to maintain optimal dental health. Keep in mind that the definition of what “regular” visits mean will vary from person to person, so it’s best to talk to your dentist to determine your ideal frequency.

2. Maintain your at-home dental hygiene routine

Maintaining your at-home oral hygiene routine is also key in preventing unwanted bacteria from flourishing in your mouth. The American Dental Association (ADA) recommends brushing your teeth twice daily with fluoride toothpaste for a total of two minutes, or 30 seconds per quadrant of the mouth or four seconds per tooth, and flossing once per day.

Ideally, though, Dr. Kalasho recommends brushing your teeth three times a day after meals—in the morning, midday, and before bed—and flossing twice a day after lunch and in the evening. (If you frequently drink apple cider vinegar or lemon water, just remember that you’ll want to wait 30 minutes before you brush to prevent dental enamel erosion).

3. Consider using string and water flossers

To optimize your flossing routine, the best floss to use are both string and water flossers, beginning with string floss first. “Flossing first allows toothpaste to reach all the spots of your teeth,” says Dr. Kalasho, while “water flossing goes almost three to four millimeters deeper below the surface of the gums than flossing [with string].”

She adds that water flossing is particularly important for people with gum disease or who are rehabilitating from gum disease. The proper technique is a must, too, particularly when it comes to using string floss. According to Dr. Kalasho: “The best way to use floss is to hug both sides of the teeth [with the floss] and resist a quick in-and-out motion. You want to make sure you take your time with it. Make sure you keep flossing until you see nothing on [the floss].”

Frequently asked questions

Why is there a bad odor when I floss?

There are a number of factors that might cause foul-smelling floss. For one, it could be that there are food particles stuck between your teeth, says Dr. Khan. If the smell is persistent, other reasons might include a broken filling, tooth decay, gum disease, or halitosis (aka bad breath), all of which would require a visit to the dentist.

Why do the spaces between my teeth smell?

If the spaces between your teeth smell, it might be that there were leftover food particles or built-up plaque, but according to Dr. Khan, it could also be indicative of tooth decay, which can likewise lead to bad-smelling floss—and bad breath.

Why does my floss smell when I floss my crown?

One possible reason why your floss smells when you clean around a crown is tooth decay. In addition to a foul-smelling odor, floss that gets stuck when cleaning your crown could also be indicative of this, says Dr. Khan. Regardless of what’s causing it, it would be best to see a dentist to figure out the best course of action.