Merck Manual

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Some Causes and Features of Bad Breath

Some Causes and Features of Bad Breath


Common Features*


Disorders in the mouth (oral)

Bacteria on the back of the tongue

Unpleasant-smelling tongue scrapings

Healthy gums and teeth

A doctor’s or dentist's examination

Affected gums and teeth noted during the examination

In people with a history of poor oral hygiene

A dentist’s examination

Cancers of the mouth (most are identified during a doctor's or dentist's examination long before they cause bad odors)

Usually identified during the examination

More common among older people, who often have an extensive history of using alcohol and/or tobacco

Biopsy, CT, or MRI

Disorders outside the mouth (extraoral)

A foreign object (body) in the nose†

Often a pus-filled or bloody discharge from the nose

Seen during the examination

Usually in children

A doctor's examination

Sometimes imaging

Cancer of the nasal passages and upper throat†

Discomfort when swallowing

A doctor's examination

Cough that produces blood or sputum (phlegm)


Chest x-ray

Cultures of sputum

Imagined halitosis (psychogenic halitosis)

Unpleasant smell not detected by others

Often in people known to exaggerate other normal body sensations

A doctor's examination

Sometimes a consultation with a psychologist

Sinus infection†

A pus-filled discharge from the nose

Face pain, headache, or both

A doctor's examination

Sometimes CT

Spitting up of undigested food (regurgitation) when lying down or bending over

Video of the upper digestive tract after barium is given by mouth (barium swallow)

Swallowed or inhaled substances

Alcoholic beverages, garlic, onions, tobacco

Apparent based on the person's history

Diagnosed after the doctor's examination rules out other causes

A doctor's examination

Avoidance of the substance to see if symptoms go away

* Features include symptoms and the results of a doctor's or dentist's examination. Features mentioned are typical but not always present.

† The odor is typically more noticeable from the nose than from the mouth.

CT = computed tomography; MRI = magnetic resonance imaging.