Back to the days of Hippocrates, doctors have relied heavily on smell. A diabetic's breath is sweet. Infections are foul-smelling.
Although odor still plays a role, modern medical technology has largely eclipsed the human nose as a primary diagnostic tool.
The latest research was inspired partly by the canine nose. Following up on decades of anecdotal reports, a 2004 study published in the journal Applied Animal Behaviour Science confirmed that two trained dogs correctly "reported" melanoma in several Florida patients.
When they read the study, researchers at the Monell Chemical Senses Center in Philadelphia knew that for dogs to make the distinction, these tumors must release into the air a set of chemicals that is somehow different from that of healthy skin.
Skin odor (as opposed to body odor) turns out to be a relatively unexplored field. So the first order of business was to develop a profile of noncancerous skin.
Working with dermatologists at the University of Pennsylvania School of Medicine and others, scientists at Monell, an independent research center in University City, collected and analyzed samples from the upper back and forearm of 13 men and 12 women aged 19 to 79.
The resulting inventory, published online last month in the British Journal of Dermatology, contains 92 compounds, both naturally occurring and residue from soaps and other byproducts of modern living that remained on subjects' skin.
Knowing what was present on healthy skin, the scientists repeated the process with cancerous skin to see if there was a consistent difference.
They started with basal cell carcinoma, a highly treatable, rarely fatal form of skin cancer that is usually caused by sun exposure - and, with more than 800,000 Americans diagnosed each year, provided plenty of patients to study.
