Age can be detected by smell, study

You can smell how old someone is, according to a study which found young people have a stronger and more unpleasant scent than the elderly.

Catching a whiff of someone's body odour is enough to tell you whether they are young, middle aged or elderly without having seen them, researchers found.

Elderly people's smell was the most distinctive but contrary but was also judged by volunteers to be less intense and unpleasant than that of younger people.

Researchers said the change in our smell is driven by the chemicals we release through our glands and the bacteria on our skin, which are reported to vary as we get older.

Humans, like other animals, most likely learned to identify traits like age and illness from each other's scent to help them pick a suitable mate and avoid catching disease, the scientists said.

The idea of older people having a distinctive smell is common to various cultures around the world, and is so widely accepted in Japan that the odour has its own word – kareishū.

To test whether or not it really exists, scientists from the Monell Chemical Senses Centre in Philadelphia collected a series of samples from three groups of 12 to 16 donors, aged 20 to 30, 45 to 55 and 75 to 95.

Volunteers wore special T-shirts fitted with underarm pads as they slept for five nights, after which the pads were cut up and put in glass jars.

A separate group of 41 people aged 20 to 30 was then asked to smell two jars at a time and asked which of the donors was older, as well as rating how strong and unpleasant each smell was.

Writing in the Public Library of Science journal, the researchers reported that participants were able to pick which one was older than the other significantly more often than could have happened by chance.

When asked to specify whether a particular sample was from a young, middle aged or old person they were much more successful at identifying older people.

The results "support the cross-culturally popular concept of an 'old person odour'", the researchers said.

Despite being the most distinctive, the older people's smell was also rated on average as being significantly less intense and less unpleasant than those from the other groups.

Researchers said their findings appeared to contradict people's negative ideas about the "old person smell" but admitted other factors, like smelly breath or skin, could be to blame for its bad reputation.

Dr Johan Lundström, who led the study, said: "Similar to other animals, humans can extract signals from body odors that allow us to identify biological age, avoid sick individuals, pick a suitable partner, and distinguish kin from non-kin.

"Elderly people have a discernible underarm odour that younger people consider to be fairly neutral and not very unpleasant.

"This was surprising given the popular conception of old age odour as disagreeable. However, it is possible that other sources of body odours, such as skin or breath, may have different qualities."