6 Surprising Causes of Bad Breath

Medically Reviewed By William C. Lloyd III, MD, FACS
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  • The first thing that comes to mind as a cause of chronic bad breath, also called halitosis, is poor oral hygiene. Not brushing or flossing can lead to buildup of plaque, a sticky bacterial film on your teeth. These bacteria produce the odor associated with bad breath. Poor oral hygiene also can lead to tooth decay or gum disease, which both can affect your breath. But there are other causes of bad breath that may surprise you. Learn what they are so you can best determine how to get rid of bad breath.

  • 1
    Dry Mouth
    man drinking coffee and smoking at a cafe

    You know why your morning breath is less than fresh? Because at night you make less saliva, which normally washes away food particles that cause bad breath (halitosis). But there are many causes of dry mouth that can contribute to bad breath, such as drinking alcohol or coffee, smoking, or mouth breathing. Skipping breakfast can also lead to bad breath due to dry mouth, even after you have brushed your teeth. Another problem could be that your saliva isn’t as acidic as it should be, which may cause halitosis.

  • 2
    Your Diet
    multi-ethnic teenage couple eating cotton candy

    Garlic and onions have long been on the list of causes of bad breath, and for good reason: After digestion, the odors pass through the bloodstream into the lungs, where you breathe them out. However, this is usually temporary and not considered halitosis. But other foods can cause chronic bad breath. A diet very high in protein has been linked to bad breath, as is excessive sugar. Bacteria feed on sugar, so the more you feed them, the more they flourish, causing the unpleasant odor from your mouth.

  • 3
    Some Medications
    closeup of multicolored pills

    There are many types of drugs that can cause dry mouth, which in turn leads to bad breath. These medications can be either over-the-counter or prescription drugs. Medications that often result in dry mouth include drugs to treat Parkinson’s disease, along with chemotherapy or radiation to treat cancer. Decongestants and antihistamines as well as drugs that help treat high blood pressure, depression, or anxiety disorders also may cause dry mouth and result in bad breath. Illicit drugs, such as methamphetamine, can cause severe dental problems like tooth decay, which causes halitosis. 

  • 4
    Tonsil Stones
    doctor examining mouth of senior woman

    Tonsil stones are a calcified buildup of cellular debris and trapped food particles getting stuck in the back of your mouth. While the stones themselves aren’t a medical problem, they can cause annoying symptoms, including bad breath. They are most likely to develop in people who have more crevices in their tonsils. If you have your tonsils, you have a chance of developing stones. Most people can express visible tonsil stones at home with a toothbrush or cotton swab, but if they’re affecting your quality of life in ways other than bad breath, you may consider talking to an ENT surgeon about a tonsillectomy.

  • 5
    doctor examining throat and mouth of senior patient

    Cancer of the mouth can cause bad breath. This is most frequently seen in older people who have a long history of drinking, smoking or using other tobacco products. If you have cancer in your nasal passages or in your upper throat, you may also experience halitosis, but the smell may be more apparent from your nose than from your mouth.

  • 6
    Certain Medical Problems
    male patient describing chest symptoms to doctor

    In addition to cancer, other medical conditions can also affect your breath. For example, diabetes may cause bad breath because of high glucose levels in your saliva and a buildup of ketones in your bloodstream. Liver problems and stomach disorders, such as acid reflux, can also cause bad breath. Although it’s not a common cause of halitosis, serious conditions may also affect the smell of your breath. Kidney failure, for example, can cause your breath to smell like ammonia or urine. Even a sinus infection, which can cause postnasal drip, is sometimes a source of halitosis. 

  • 7
    How to Get Rid of Bad Breath
    father and son brushing teeth in bathroom

    First, make sure you are taking good care of your mouth and have good oral hygiene. Brush your teeth twice a day, and floss daily to remove any food particles that may be stuck between your teeth. Also remember to brush your tongue, especially in the back, to remove bacteria. If you wear dentures, be sure to clean them well every day. To treat dry mouth, try drinking water, chewing gum, or sucking on candy (sugar-free, of course) to help you produce extra saliva. If you have a medical condition that’s causing bad breath, work with your doctor to address that underlying issue. Your dentist can also provide advice on what remedies might work best for you.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 13
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.