Actually, by avoiding certain foods, he can.

A nutrient called choline is especially prevalent in eggs, liver, certain seafoods and legumes such as soybeans. Bacteria break it down in the large intestine, producing a fishy-smelling chemical called trimethylamine.

In most people, the byproduct is oxidized by the liver and excreted as odorless waste. Those with trimethylaminuria, however, have a faulty version of a key liver enzyme. Though otherwise healthy, they are unable to oxidize the smelly trimethylamine, which is excreted in their urine, sweat, saliva and breath.

Some patients, including Mike, can keep their odor under control by avoiding foods high in choline. "I miss sushi in a big way," Mike says.

For others, Preti also recommends copper chlorophyllin complex, a supplement that appears to take up excess trimethylamine.

Antibiotics also can provide temporary respite. But Preti follows a specific treatment sequence and urges people not to try things on their own.

Even after all this, some patients still have a problem. Preti so far is at a loss for what to suggest, although he is looking for answers.

Genetic clues

As a graduate student at the Massachusetts Institute of Technology, he analyzed dust samples from the Apollo 11 and 12 missions to the moon.

After landing a job at the Monell Center in 1971, his pursuit of chemistry took an earthier direction: bodily secretions. He won acclaim for studying pheromones and went on to discover the key chemical in human underarm odor.

In the late 1980s, a New York clinic referred a patient who complained of an occasional fishy taste in her mouth.

Preti recalled that Fennessey, whom he knew from grad school, had run across a similar case and had determined that his patient had trouble metabolizing trimethylamine. They spoke, and a collaboration was born.

The patients come to Philadelphia for three hours of consultation and tests. Their urine samples go to Colorado, where Fennessey's lab has developed a way to screen for the condition. Preti remains the only specialist in the United States who sees such patients, says Sandy Gordon, who saw Preti and later helped create the Trimethylaminuria Foundation.

Gordon, whose version of the disorder gives her a pungent smoky odor, almost moved out of her New York apartment in shame after fellow tenants incorrectly attributed her smell to marijuana smoke.

She went from specialist to specialist, and despaired after reading materials that suggested some patients imagine they have a disorder. Ten years ago, she heard of Preti.

"It was literally a turning point in my life," Gordon says.

More common than Gordon's smoky odor, but still rare, are the patients who smell like fish. Reports have appeared sporadically for centuries. In Shakespeare's The Tempest, Caliban is described as having "a very ancient and fish-like smell."

Yet only in the past few decades have scientists shed light on a cause. In 1972, researchers identified the lack of the correct liver enzyme as a culprit.

In 1997, British scientists found genetic mutations that lead to the disorder.