Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum Liquid L Carnitine Core Nutritionals Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish. Body odor decoded! A skin resident bacteria, Staphylococcus hominis, transforms sweat gland metabolites into sulfur containing compounds associated with body odors like those from onions via a two step process. In a recent Journal of Trimethylaminuria: Understanding and Treating Fish Odor Syndrome