You know how old people smell kind of, well, old?

(Linda Davidson/The Washington Post)

Research conducted at the Monell Chemical Senses Center in Philadelphia had 41 young people ages 20 to 30 sniff body-odor samples collected from 41 donors from three age groups: “young” (20-30 years old), “middle-age” (45-55) and “old-age” (75-95).  They were asked to rate the scents’ intensity and pleasantness, determine which ones came from old donors, and estimate the age of each sample’s donor.

The samples were gathered via pads affixed to the underarms of T-shirts that the donors wore every night for five nights. Steps were taken to keep other smells, such as those from soap, detergent, cologne, medications or spicy foods, from skewing the scents. To ensure that the evaluators weren’t swayed by any one person’s individual scent, each pad was cut in four and combined with other samples from the same age group in a jar. (Add underarm pad-cutting to the list of jobs I am glad are not mine.) The various jars were presented as samples for evaluation.

The young sniffers correctly identified the age groups from which the sample sets were taken. They were better able to guess the ages of the people from the old group than younger donors’ ages. And while they found the scents from the older people’s armpits distinctive, they didn’t find them unpleasant or intense. By contrast, they did find many of the samples from young and middle-aged people intense and/or unpleasant. Also, while they could judge the gender of the donors in the young and middle-aged groups, they weren’t able to distinguish male from female among the old donors.

The study, published in the journal PLoS ONE, notes that people’ s skin biology and chemistry change as they age, which may account for changes in the way their skin smells. They also point to animal studies showing that creatures other than humans discern age differences among other members of their species on the basis of their scent. The authors suggest that body odor might offer animals important clues about potential mates’ worthiness for reproduction.

The authors note that we likely experience people’s scents differently when we are actually near them, not just sniffing their underarm pads in a jar. “[I]n everyday life ,the old age odor is experienced in the context of an old individual being present,” the study says. Because research has shown that the way an odor is labeled strongly influences people’s perception of that odor, “it is likely that the body odors originating from the old individuals would have been rated as more negative if participants were aware of their true origin.”

Which doesn’t sound like something to be especially proud of.