Every time you breathe out, you release small amounts of chemical compounds produced by your organs. When disease shifts the body's chemistry, the smell of the breath can shift with it.
A 2023 review in Molecular Diagnosis & Therapy calls this field breathomics, noting that "a small but significant change in VOC spectrum" appears when a person moves from health to disease.
That is why physicians have long paid attention to breath odor. A few smells are strong enough that clinicians treat them as clues to organ trouble. Here is what four of them can mean.
Fruity breath and uncontrolled diabetes
A sweet, fruity or nail-polish-like odor is a classic sign of diabetic ketoacidosis, a dangerous complication of poorly controlled diabetes. When the body cannot use glucose for fuel, it starts burning fat instead and releases chemicals called ketones.
Also read: 80 minutes less sleep may affect your weight
One of those ketones is acetone, described by Medical News Today as "the same fruity-smelling substance found in some nail polish removers."
Cleveland Clinic warns that low insulin "can put you at risk of a medical emergency called ketoacidosis. It can make your breath smell fruity." The condition can develop quickly and needs immediate medical care.
Ammonia breath and the kidneys
Breath that smells sharply of ammonia or urine can point to the kidneys. Doctors call it uremic fetor, and it appears in advanced chronic kidney disease when the organs can no longer clear urea from the blood.
According to Fresenius Kidney Care, excess urea in the body reacts with saliva to form ammonia, which is then exhaled. Cleveland Clinic adds that kidney and liver disease "may prevent these organs from filtering toxins out of your body as they normally do. The effects can show up as halitosis."
Also read: The Finnish walking technique that may ease depression in just five weeks
Musty or garlic-like breath and the liver
Liver disease has its own signature odor, known as fetor hepaticus. Cleveland Clinic describes it as "musty, pungent, oddly sweet and occasionally fecal," often compared to a mix of rotten eggs and garlic.
The odor comes from sulfur compounds that a healthy liver would normally break down. Dimethyl sulfide carries a garlicky smell, and methyl mercaptan smells more like rotten eggs.
In advanced cirrhosis, blood bypasses the scarred organ and these compounds reach the lungs. Cleveland Clinic calls the smell "a sure sign that you should see a healthcare provider."
Persistent bad breath despite good hygiene
Not every stubborn case of bad breath signals organ disease. But if careful brushing and flossing do not solve it, the cause may lie elsewhere in the body.
Also read: Why some farts smell so much worse than others
Sleep apnea is one candidate. "People with sleep apnea are at increased risk for bad breath," Dr. Maureen Theresa Butler told Northwestern Medicine. The condition forces mouth breathing at night, drying the saliva that normally rinses away odor-causing bacteria.
Gastroesophageal reflux disease is another possibility. Cleveland Clinic notes that GERD "causes stomach acid to leak back into your esophagus and, sometimes, your mouth. The fluid may taste sour and smell bad."
When to see a doctor
Most bad breath starts with bacteria on the tongue and teeth or a dry mouth, not a systemic illness. Cleveland Clinic advises that if good hygiene does not clear halitosis, patients should see a dentist first. If no oral cause is found, a primary care physician can look for another condition.
An acetone-sweet exhale in someone with diabetes, an ammonia note during kidney trouble, or a musty garlic smell alongside liver disease is different. These are signals that deserve prompt medical evaluation, not panic.
Also read: Which vaccines are worth considering? It depends on your age
Also read: 8 warning signs of fibromyalgia that are often dismissed as normal pain
This article is made and published by Jesper Bengtson, who may have used AI in the preparation.