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What to do if your floss or tooth smells bad after flossing

floss pick in between teeth

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

The National Health Service (NHS) 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.

Teeth with bleeding gums

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

Decaying Tooth
Source: Wiki Commons

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 

floss in between teeth

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.

About Gemma Wheeler

GDC number: 259369. Gemma qualified from Cardiff University School of Dentistry with BDS(Hons) in 2015. She went on to complete her Foundation Training and a further two years in the Armed Forces, primarily based around Wiltshire. She now works in a private practice in Plymouth.

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2 thoughts on “What to do if your floss or tooth smells bad after flossing”

  1. I have 3 or 4 cavities, and my dentist wont do any fillings because he says my braces are making it a bit difficult. He says they arent actual holes, they’re just a bit black, but i feel that i have bad breath because of them. Do you know what i can do to keep my cavities clean ig until i take my braces off?

    • Hi Iliana,

      It can sometimes be okay to leave black marks on teeth if they are arrested caries/decay. I can’t comment on whether or not this is right for you as I haven’t examined you in the clinic. But if you have got any concerns about whether they should be left or not, do ask for a second opinion. This could be from another dentist in the same practice.

      When it comes to keeping them clean, you want to do everything you can to prevent them from worsening. This is a combination of reducing your sugar intake and cleaning effectively. Cleaning will remove the decay-causing bacteria and will introduce fluoride that helps with rehardening (remineralising) the enamel layer.

      Keep any sugary food and drinks to meal times only.

      Clean your teeth and braces after each meal. Use either an electric toothbrush or a manual brush. Also use a fluoridated toothpaste when brushing. Afterwards spit, but don’t rinse – this lets the toothpaste have a good effect. You could also talk to your dentist about prescribing you a strong toothpaste if they think it is appropriate- Duraphat toothpaste comes in 5000ppm (instead of the max of 1450ppm available in shops).

      Use interdental cleaners to clean around the brackets and in between the teeth.

      Using a fluoridated mouthwash once a day will also help prevent decay. Do it at a different time to brushing though, otherwise you are washing off your toothpaste! We also have some more information about that here.

      Hope these tips help.


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