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 When a 12 month old boy in Portugal developed an unexpected and persistent smell similar to rotting fish, his parents were unsettled. The child appeared healthy, showed no signs of infection, and behaved normally. What is Carnitine? Does Carnitine Cause Body Odor? Lume Deodorant