It’s isoprene. That’s what these dogs are smelling—a common natural chemical found in human breath.

The scientists recruited eight women with type 1 diabetes, and under controlled conditions, lowered their blood sugar levels. Using mass spectrometry, they looked for specific chemical signatures to detect the presence of certain molecules. Looking at the data, the researchers found that isoprene rose significantly during hypoglycemia (the medical term for critically low blood sugar levels). In some cases, the presence of isoprene nearly doubled.

Humans are oblivious to isoprene, but the researchers figure that dogs are particularly sensitive to the chemical, and can easily tell when their owner’s breath contains too much of it. As to why the body produces more isoprene during hypoglycemia, the researchers think it’s a byproduct of cholesterol production. Still, they’re not entirely sure why this chemical rises when blood sugar gets low.

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Using this knowledge, the researchers would like to develop a medical sensor that does the same thing as diabetes sniffing dogs. What’s more, a handy breath device could replace the current finger prick test, which is inconvenient, painful, and relatively expensive.

It’s important that we don’t overstate some of the purported abilities of medical detection dogs. They seem to be pretty good at detecting certain cancers (e.g. urological cancers and breast cancer) and diabetes, but many of these accounts are anecdotal, and much of the research tied to these canine abilities is still in early stages. Claims that dogs can sniff out lung cancer, colorectal cancer, and even Parkinson’s Disease are still under investigation and are far from proven.

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Still, it’s an exciting line of medical research that, like this recent study, could lead to new scientific insights and powerful new medical technologies.

[Diabetes Care]