Taking the dog out for a swim seems like a great idea, right until he emerges wet and stinky. Why does he smell so bad when he’s wet? With the help of chemistry and biology, we find out why!

When you take Fido out for a walk, there are a whole lot of microorganisms that will find their way to his fur, and there. While dwelling in their new furry home, they produce a range of volatile organic compounds, and these compounds produce stinky odours when in contact with water.

Water helps to break down the micro-excreta of the bacteria and yeast in the dog's hair. As the water evaporates, it carries with it some of the volatile compounds, and that’s when the smell reaches your nose!

Water evaporation increases the humidity of the air surrounding Fido, and because humid air is able to adopt a higher concentration of smelly molecules, the effect is intensified, making your pooch seem like he hasn’t showered for months.

There’s no one specific molecule that causes our pups to stink. Instead, it’s a combination of molecules that make up the smell. The individual molecules have different smells, but when combined, creates the typical “wet dog smell”.

*This article was updated on 5 Oct 2020. It first appeared in PetsMagazine.com.sg on 14 July 2016.