Johan Lundstrom, a 46-year-old biologist with the Monell Chemical Research Center, says his studies confirm what Japanese researchers found in 2001: An unsaturated aldehyde called 2-nonenal is more concentrated on the skin of older people, often producing a distinctive grassy, waxy or fatty odor.

His study — admittedly small — used samples from the underarms of people from the ages of 20 to 95 and presented them to 41 participants who ranked them on intensity and unpleasantness. In addition, Dr. Lundstrom and his co-authors found that “participants were able to correctly assign age labels to body odors originating from old-age donors but not to body odors originating from other age groups.”

But George Preti, a 74-year-old analytical organic chemist, also with the Monell Chemical Research Center, says his studies did not match the results found by either the Japanese group or Dr. Lundstrom’s team. Dr. Preti’s team used upper back and forearm samples and submitted them to gas chromatography and mass spectrometry, concluding that “no method of analysis” revealed the presence of 2-nonenal in older subjects.