You definitely have smelled it before, Whether it’s your grandparents or complete strangers, old people have a very specific smell. Some people describe it as musty, others – as stale of even medical. But what causes it? And why so many older people smell so alike?
Well, part of the reasons of course are related to their lifestyle. They are usually not in a good health and so they consume lots of medicine and don’t take good care of themselves. It may be also some older clothes or old, dusty items in their homes. There are many reasons why older people don’t smell particularly nice. However, some of them are actually biological.
Japanese call this smell kareishu. Because Japan is famous for its respect for elderly and rapidly ageing population, it comes as no surprise that they also research older people quite a bit. In one study researchers asked 22 people, aged between 26 and 75, to wear special shirts that collect smell. Then researchers analysed the compounds in these shirts and compared data from younger and older people. They found that the amount of 2-nonenal was three times as prevalent in the oldest participants than in the middle age group. The youngest participants produced very little 2-nonenal.
Scientists believe that the increase in 2-nonenal is related to the breakdown of omega-7 unsaturated fatty acids. As omega-7 deteriorates with ageing, 2-nonenal is released as a byproduct and seeps through the skin. The good news is that it's washed away. The bad news is that it comes right back. The smell of the 2-nonenal has been described as “greasy” or “grassy” odour, which matches what old people smell like.
And they do smell. In another research scientists gave participants some shirts to smell. They had to recognize person from which age group was wearing a particular shirt. They could only go by smell, but still managed to identify the scent of old people (75- to 95-year-olds) without any trouble. Meanwhile body odour from other groups was difficult to recognize.
In our modern society body odour is an unpleasant thing. We don’t want other people to smell anything else but perfume or cosmetics. However, our ancestors probably were very happy that older people smelled this way.
“Old people smell” could help identifying unsuitable mating partners. Surely, you can tell that by their appearance too, but back in tribal communities people were mating left and right with everyone from different age groups. Of course, the goal was always to spawn offspring, which is why the smell of older people was so useful.
Not so much anymore. 2-nonenal is a product of other chemicals breaking down. Once the body starts slowly getting rid of its functions, there are more such compounds. Just be tolerant – one day you will have kareishu too.