Is sweat from exercise different from that due to anxiety or illness?

Not only does sweat have a different chemistry when it arises from stress, illness or exercise, but dogs can tell the difference. And so can super-smellers – people with an incredibly sensitive sense of smell

1 February 2023

A man holds his lurcher dog as the canine excitedly licks and nuzzles with a woman who smiles and strokes the pet. — Catherine Falls Commercial/Getty Images

Is sweat from a different cause – such as exercise, anxiety or illness – chemically unique? Can dogs tell the difference?

Claire Guest,

Medical Detection Dogs, Milton Keynes, UK

In short, yes. Sweat is mostly composed of water, but it also plays a role in the excretion of toxins and waste products from the body.

These substances can be hormones, minerals or volatile organic compounds (VOCs) produced as a by-product of disease. They can vary from person to person and depend on the cause of perspiration.

For dogs, which possess up to 300 million olfactory receptors, sniffing out the difference can…