"Old people smell" is real

You know the odor of retirement homes, synagogues on high holidays, churches on crowded Sundays, and, perhaps, your grandmother's house? Turns out that "old people smell" seems to be a real thing, according to a new scientific study. Neuroscientist Johan Lundström of the Monell Chemical Senses Center led the study that involved people of various age groups wearing underarm pads as they slept. Then, a separate group of young adults smelled bits of the pads and consistently identified those that came from the 75-90 age group.

From CNN:

The root cause of the old person smell is still a mystery, but the study notes that long-term changes to the skin glands may be involved. Lundström suspects it also may be related to an accelerated rate of cell decay. "As cells die at a faster pace, they might give off a different odor that is unique to people with old age," he says.
Another possibility is that the scent indicates an undiagnosed illness. Although the study participants were all outwardly healthy, some may have had underlying ailments that come naturally with old age, Lundström says.

"Scientists confirm existence of 'old person smell'"