Old people do have a particular smell and it is nicer than the scent of younger people.
Researchers have conducted an experiment that shows humans - like other animals - can detect social information, such as how old others are, by their scent.
Armpit odours, from pads sewn into T-shirts, were collected from volunteers of young, middle-aged and old participants.
The donors had to wash nightly with odourless soap and shampoo, had to avoid spicy foods, cigarettes and booze and sleep alone in their T-shirts for five consecutive nights.
Each day the T-shirts were stored in airtight bags, said the researchers, led by Johan Lundstrom of the Monell Chemical Senses Center in Philadelphia, Pennsylvania.
Their paper, printed in the journal PLoS ONE, said the donated smells were evaluated by people who were asked to rate the intensity and pleasantness of each odour, identify which of two scents came from the older individual, and estimate the age of the individual who produced each sample.
Dr Lundstrom said the participants were able to discriminate between the three donor age categories and there really was a distinct "old person" smell.
"But old person smell is less intense and less unpleasant than body odours of middle-aged and young individuals," he said.
"This was surprising given the popular conception of old age odour as disagreeable."
Dr Lundstrom said this might just be their armpits.
"It is possible that other sources of body odours, such as skin or breath, may have different qualities," he said.