Fish odour syndrome CMAJ Trimethylaminuria, or fish odour syndrome is an uncommon condition that causes an unpleasant, fishy smell. The body is unable to turn a strong smelling chemical called trimethylamine produced in the gut when Trimethylamine N oxide (TMAO): Pathway, Cardiovascular Risk, Diet & LCMS MS Testing L carnitine supplements can cause a fishy odor in the breath, sweat, and urine. This is likely due to the formation of trimethylamine (TMA). TMA is also responsible for the pungent smell of Ever heard of Fish Odor Syndrome? Its a rare condition where the body cant break down trimethylamine a compound found in foods like fish, eggs, and beans. This leads to a strong, fish like smell L Carnitine Side Effects & Safety: A Complete Guide The Science of Good Health