Researchers Nose Into the Smell of Sickness

You may have an illness and not even know it—and the proof could be on your breath. That's because our bodies give off complex aromas, some too faint for a human nose. And when sickness alters cell metabolism, an array of telltale volatile chemicals make their way into our breath, urine, and sweat. Now, research labs around the world are figuring out how to use gas sensors to detect disease. Here are a few ailments they've gotten a whiff of so far.

• Lung Cancer

  Breath odor: Ammonia, fish
  Source: Methyl hydrazine
  Detection: A grid of gold nanoparticles, each with different chemiresistive organic coatings. Certain volatile chemicals cause the sensor's particles to swell, changing their electrical resistance and allowing scientists to identify signs of cancer on a patient's breath.

• Preeclampsia

  Breath odor: Lighter fluid
  Source: Undecane, 6-methyltridecane, 2-methylpentane, 5-methyltetradecane, 2-methylnonane
  Detection: Gas chromatography/mass spectrometer. The instrument can spot markers of runaway oxidation in a pregnant woman's body, an indicator of preeclampsia.

• Ketoacidosis

  Breath odor: Rotten apples, nail polish remover
  Source: Acetone
  Detection: Polymer sensors. Acetone is produced by the liver when sugar-starved cells shred fat to make energy. In theory, the sensors could be built into cheap, pocket-sized gadgets that tell diabetics when to take insulin.

• Schizophrenia

  Breath odor: Ether
  Source: Carbon disulphide
  Detection: Ion trap mass spectrometer. If someone is certifiably nuts, their breath may have notes of ether and pentane, according to one study. Unfortunately pentane appears in high levels with all sorts of disorders, so it's not a reliable marker.

• Urinary Tract Infections

  Urine odor: Cheese, locker rooms, feet
  Source: Isovaleric acid
  Detection : Electronic nose. Equipped with 14 different types of conductive polymers, the synthetic sniffer can distinguish between infections caused by E. coli, staph, and proteus parasites.

• Melanoma

  Skin odor: Gasoline
  Source: Nonane, phthalate, butanal, dimethylsulfone, indole
  Detection: Gas sensor array. Researchers have developed a device that can analyze the volatile chemicals emanating from a tissue specimen tube to determine whether the sample is cancerous.