Why does it smell when i floss

You're happily going through your bedtime routine: a hot shower, indulgent multi-step skincare ritual, teeth brushing—you know the drill. And because you understand the importance of flossing, you also pop out a string of floss to remove any food between your pearly whites. But then you realize, post-flossing, that your floss has a funky smell. So, what does this mean? 

Let's start here: the American Dental Association recommends (ADA) recommends flossing, also referred to as interdental cleaning, to help remove debris and plaque that gets trapped between teeth, reducing the risk of gum disease and tooth decay. Stinky floss might indicate that there are decaying food particles between your teeth—hence the need for regular flossing. However, in most cases, smelly floss might be a sign of bacteria "building below the gum line, where your floss and brushing cannot reach," says Rhonda Kalasho, DDS, doctor of cosmetic dental surgery and CEO of TruGLO Modern Dental, adding that this can also happen under a restoration like a crown or filling.

Dr. Kalasho says two common bacterial organisms could be culprits: porphyromonas gingivalis and treponema denticola. These two are typically found in active gum disease, she says. They have an unpleasant smell and release toxins and enzymes that elicit an inflammatory response. 

If left untreated, the growing bacteria can cause issues such as bad breath, infections, gum inflammation, bone loss, and tooth loss, Dr. Kalasho adds. So, if you do get a funky whiff after flossing, she recommends paying a visit to your dentist ASAP to get it checked out and prevent the harmful bacteria from causing any damage. 

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Dental professionals recommend some sort of interdental cleaning once a day. You should do this as well as your brushing routine. 

The Australian Dental Association (ADA) considers it to be an essential part of your cleaning regime.

Flossing is one type of interdental cleaning method – one way of cleaning between your teeth.

Other options include using a water flosser or interdental brushes — find out how the various methods compare here.

But for the sake of this article, the term flossing refers to any one of these types of interdental cleaning, not just string floss.

Sometimes when you floss, it creates a bad smell. 

You might be thinking “why does my floss smell after using it?”.

Or maybe you think that your breath smells after flossing. Well, read on to find out the possible causes and what you can do about it.

The reasons floss can smell bad after flossing

In the section below I outline some of the reasons your floss can smell bad when you’ve finished using it.

Remember to seek the advice of a dental professional if something consistently troubles you.

Old Plaque And Food Stuck Between The Teeth

The most common reason for floss to smell after use is that you have days old plaque and food on it. 

Trapped plaque and food starts to smell due to the bacteria present. 

Floss pulls plaque off the teeth. It also dislodges any food debris from between the teeth. This releases the smell.

Floss and brush regularly and this problem will go away.

You Are Experiencing Advanced Gum Disease

Advanced gum disease, periodontitis, is caused by bacteria. 

These anaerobic bacteria are difficult to remove because they sit well underneath the gums.

Studies link these bacteria to bad breath because they produce volatile sulphur compounds (VSCs). These VSCs are responsible for halitosis, or bad breath.

Flossing areas where there is periodontitis will release the VSCs leading to a bad smell on the floss.

A good oral hygiene regime will help manage gum disease. But you should also see a dental professional for treatment including a scale and polish.

You Have Acute Necrotising Gingivitis

Acute Necrotising Gingivitis, sometimes referred to as AUG or ANUG, is a severe infection of the gums.

A study in The Journal of The Canadian Dental Association (JCDA) links the infection to specific bacteria, which is different to plaque induced gingivitis.

If you have this infection your gums will be very sore, with lots of ulcers, and with bad breath too. 

You will notice that the floss will smell when you use it. You need to visit the dentist if you think you have this condition as you will need some treatment.

There Is Dental Decay In Your Mouth

Dental decay is another common source of bad breath.

Dental decay leads to holes in your teeth. These holes are a perfect hiding place for the bacteria which release VSCs, causing bad breath.

When you floss you will release these VSCs, leaving a bad smell on your floss.

These holes will also store rotting food, which will smell on your floss as you remove it.

Treating the dental decay with fillings will remove the source of the bacteria and food. This should stop your floss smelling when you use it.

You Have A Loose Filling

Loose fillings provide hiding places for bacteria and food. This is the same process as for dental decay. 

The smell from these will rub off on your floss when you use it. The odour is likely to affect only one tooth.

If you have a loose filling you might also notice that your gums bleed when flossing, or that you get floss stuck in that area.

See a dental professional who can replace any loose fillings, and the problem should go away.

What steps to take 

Good oral hygiene is the key to stopping floss from smelling when you use it.

Regular and effective removal of plaque and food debris will stop them staying long enough to cause a smell.

If your floss smells after flossing take these steps to keep the gaps between your teeth clean:

With good cleaning, the problem should resolve within one to two weeks. 

But if it continues you should see a dental professional.

A dental professional can tell you if there is dental decay or a loose filling present. They can provide treatments for these. 

Seeing a dental professional can also help you manage advanced gum disease.

Does it mean you have bad breath if your floss smells? 

Not always.

It is possible to have a bad smell on your floss without suffering from halitosis (bad breath).

It is also possible to have halitosis and not notice until you start flossing.

A bad smell on floss doesn’t equal bad breath

Even if your floss smells after flossing, you do not definitely have bad breath (halitosis).

Floss irritates pockets of bad smell and removes rotting food. These might be in very small areas of the mouth.

If only a couple of gaps between your teeth have disease, it is unlikely that your breath will smell.

Halitosis is a longer term problem that you can talk to your dental professional about.

But bad smelling floss can be an indicator of bad breath

Slot et al point to the fact that bad breath is caused by a problem in your mouth in over 75% of cases. 

The most common causes of bad breath are gum disease and dental decay.

If you have recently started to floss as you pay more attention to your mouth. A strong smell on your floss may be the first sign you notice of bad breath.

This is possible because you have become immune to the smell of your own breath. This is normal.

Ask a person you trust if they think you have bad breath.

The Bottom Line

The take home message is that bad smelling floss occurs because of bacteria causing decay or gum disease.

Bad smelling floss can tell you there is a problem in only one area. Or it could alert you that you have halitosis. 

But the fact that one area smells when you use floss does not always mean that you have bad breath.

Manage bad smelling floss by cleaning between the teeth and seeking advice from a dental professional if you are concerned.