Trimethylaminuria is a rare genetic disorder in which the body is unable to break down the chemical compound trimethylamine. The latteris produced by bacteria in the intestines during the digestion of proteins from eggs, liver, legumes such as soybeans and peas, some varieties of fish, and other foods. Normally, an enzyme breaks down trimethylamine, which has an odor that's been likened to rotting fish or eggs, garbage, or urine [source National Library of Medicine].
But people with trimethylaminuria, because of a mutation in the FM03 gene, either lack the ability to produce the enzyme or make too little of it. In a few cases, even people with the normal gene can develop a similar odor, because of an excess of dietary protein or liver or kidney disease [source: National Library of Medicine]. The result is that patients give off a very strong fish-like smell. There's no cure for trimethylaminuria, but people may be able to curb the odor by avoiding the products listed earlier and taking certain supplements and antibiotics [source: NIH].