Asparagus makes your pee smell due to asparagusic acid, which is found exclusively in asparagus. When you eat asparagus, the asparagusic acid gets broken down into sulfur byproducts during digestion. As anyone who has ever smelled a rotten egg knows - sulfur is stinky. The sulfur byproducts evaporate into the air almost as soon as you begin to pee, which is why you can smell them. That's the scoop on "asparagus pee."