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 Supplements & Body Odor ConsumerLab.com 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 Ultra L carnitine making me reek of rotting fish for 48 hours #lcarnitine #fishy #smell #trauma #fyp