While bad breath is unpleasant in any form, keto comes from a different source than most chronic bad breath. And it has a different smell and “taste.”

Most chronic bad breath is caused by bacterial overgrowth in the mouth. This type of bad breath has a really stinky odor, quite often smelling like rotten eggs due to the sulfur gas given off by the bacteria.

But keto breath has a smell that some people compare to nail polish remover together with an unpleasant fruity odor. Often people experience a metallic taste in their mouths as well. And while not everyone on keto diets experience this, it is a good sign that the diet is working and that your body is in ketosis.

What causes keto breath?

When you shift your diet over to a super low-carb intake you force your body to stop those fast-burning carbs for fuel and to start breaking down fat for fuel. This process produces byproducts known as “ketones” which the body gets rid of by urination and breathing.

One type of ketone, actually the simplest ketone, is called “acetone” which might sound familiar as it is the main ingredient in nail polish remover. Acetone has a very powerful and sharp smell which is associated with keto breath.

The good news is that keto breath generally goes away, or at least diminishes, as your body gets more efficient at burning fats instead of sugars.

But, while you have it, keto breath can be pretty annoying and unpleasant, especially if combined with even a light case of bacterial foul mouth.