Asparagus makes urine smell because it contains a unique chemical called asparagusic acid. When the body digests asparagusic acid, it breaks it down into several sulfur-containing compounds. These sulfur compounds are volatile and evaporate quickly, producing a strong, distinctive, and often unpleasant odor in urine similar to the smell of rotten eggs or sulfur. The smell can appear as soon as 15 to 30 minutes after eating asparagus and typically lasts for several hours. Not everyone can detect this odor due to genetic variations affecting the ability to smell it, and some people may not produce the odor even if they consume asparagus.