CONTRARY TO WHAT your mother always told you about cleaning up before visiting the doctor, do not brush your teeth or take a shower if you want to provide every possible clue to your medical condition. A serious lung abscess was diagnosed because, although the patient had none of the associated risk factors and early tests came back negative, his wife kept insisting that his breath was “different. Not bad, but it’s changed. Something is not right.”
Scent can provide tip-offs to medical conditions from cancer, in particular melanoma; infectious diseases including pneumonia and tuberculosis; schizophrenia and diabetes to more common conditions like strep, sleep apnea and GERD (gastro-esophageal reflux disease).
In the sweat, melanoma gives off an odor like gasoline, and schizophrenia is associated with a musty or sweet smell, or like overripened fruit. From the breath, diabetics can smell like acetone and rotten apples, and strep smells metallic. Because the liver and kidneys are used to clean blood, any partial shut-down due to disease can make the breath smell fishy. Although people generally aren’t aware of their own odors, sinus infections can be detected when the sufferer believes they smell a dead animal nearby. (I have searched my kitchen several times.)
The ability to identify odors varies among cultures, with English speakers, for example, less adept at naming the smell of cinnamon or ginger root compared to rain-forest foragers on the Malay Peninsula.
Artificial electronic noses offer a “fast, noninvasive and practical everyday diagnostic tool,” according to papers presented at recent medical conventions. Breath tests using the Cyranose 320 correctly identified 96 percent of patients with cancer, with a 9 percent false positive rate among non-cancer patients. Using technology that is now considered old-school (gas chromatography-mass spectrometer, which can detect tiny amounts of specific substances), profiles of patients with lung disease found levels of four organic compounds higher than normal in patients with pneumonia and lower than normal in those with cancer. First noted in the 1870s, the musty smell of schizophrenia was confirmed by GC-MS.
Less high-tech, service dogs can detect blood sugar changes in their diabetic owners and can alert them if they are about to have a seizure. Dogs have also been known to lick or bite at parts of their owner’s skin that turned out to be melanoma.
In the fancy-if-not-yet-available tech arena, surgical knives can use smell to determine whether they are cutting through healthy or cancerous tissue, and robots can detect explosives via the smell, recoil at the smell of a person’s breath and detect explosives.
And then there’s the Alzheimer’s disease smell test: Put a little peanut butter on a spoon and compare the distance at which you can smell the peanut butter, first from the left nostril with the right nostril blocked, and then from the right nostril. If the point at which you first detect the odor from your left nostril is six centimeters or more farther away from you than it is from the point detected by the right nostril, you can begin to worry.