The 6 list: Causes of bad breath

“The 6 list” is a recurring feature exploring various topics on oral health, curated for both patients and dental professionals to share with their patients. “6 causes of bad breath” was medically reviewed by David R. Rice, DDS, chief editor of DentistryIQ.


Halitosis, or bad breath, is tricky because for the most part, you don’t even know when you have it. And if it gets to the point where you’re being told about it, it’s probably been going on for a while.

If left unchecked, bad breath can impact your social and work relationships—not to mention the fact that often it’s linked to a dental or health issue that you need to address. Here’s a look at six common reasons for halitosis/bad breath.

Poor oral health/hygiene

If you don’t stay on top of brushing and cleaning between your teeth, a sticky film of bacteria—plaque—forms on the teeth. If not brushed away, plaque can irritate your gums and eventually form pockets between your teeth and gums (periodontitis). Plaque that isn’t removed from teeth turns into tartar, a sticky residue that can’t be removed by brushing. Your tongue also can trap bacteria that produce odors.

dry mouth

Dry mouth, or xerostomia, is a huge cause of and contributor to bad breath. The reasons for dry mouth range from medications and tobacco use to age and stress. For those with dry mouth, figuring out the cause and treating it will likely improve halitosis.

Tobacco products and marijuana

The effect of cigarettes and other tobacco products on breath are varied: they cause a decrease in saliva, leading to dry mouth. The smell of the smoke itself (in cigarettes or marijuana) also lingers and causes bad breath. What’s more, smoking is a leading cause of gum disease—another source of odor from the mouth.

Foods (not just the obvious offenders)

Everyone knows garlic and onions don’t help with fresh breath, but there are more dietary culprits than those. Other foods that can contribute to bad breath include an abundance of protein, cheese and other dairy products, peanut butter, and coffee.

Sinus and throat issues

Sinus infections and postnasal drip can cause bad breath. Related, allergies can also contribute because they can lead to mouth-breathing, a main cause of dry mouth.

Other chronic health problems

It’s rare, but halitosis can also be caused by some chronic health problems such as diabetes or kidney and liver failure. Your dentist may advise you to consult your doctor if they suspect your bad breath is caused by something other than oral hygiene issues, food, or smoking.

The bottom line

If you have halitosis, treating it should start with knowing why you have it. Start by talking to your dentist and doctor.

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