The idea of using breath tests as a medical diagnosis dates back to Hippocrates. Around 400 B.C., he wrote a paper on breath aroma and disease. For many years, doctors have noticed how particular breath odors can be associated with a disease. 

Today tools called mass spectrometers can detect the tiny chemical compounds in your breath, according to Medical Daily in reference with the Wall Street Journal. Here are just a few of the many illnesses that may be revealed through your breath:

1. Lung cancer

Scientists have already known that some animals are able to sniff out certain diseases. Working off of this idea, researchers have been trying to develop an “electronic nose" technology. Tthe study suggests that it is possible for an electronic nose to differentiate lung cancer from different lung conditions and healthy people. 

2. Heart failure

One team of scientists was able to detect heart failure through an analysis of patients’ breath. The test was originally used to detect kidney failure using a breath test. The heart patients were merely used as a control. It did not take long for the researchers to realize that the heart patients also had their own unique “breath prints.” 

3. Obesity

Another study, conducted by researchers at Cedars-Sinai Medical Center in Los Angeles, found that one’s breath could show how susceptible a person is to develop obesity. Researchers analyzed the breath of 792 participants and found that those with high concentrations of the gases methane and hydrogen had higher BMIs and higher percentages of fat than those whose breath had the normal mix of gases or a high concentration of either methane or hydrogen alone.

4. Diabetes

A fruity breath odor, or one similar to nail polish, can indicate a serious problem in diabetic patients called ketoacidosis. This is a life-threatening problem that occurs when the body cannot use sugar as a fuel source because there is no insulin.

5. Kidney failure

Breath that has an ammonia-like odor can sometimes occur in people who suffer from chronic kidney failure. This smell is also described as urine-like or fishy. The kidneys remove wastes from the blood. When the kidneys fail, also known as end-stage renal disease, they are no longer able to remove toxins from the blood. Waste builds up throughout the body, and one of the ways they are released is through the respiratory system in the form of bad breath.