What causes ‘old person’ smell?

What causes old person smell? As our skin matures, its natural antioxidant protection declines. This decline results in greater oxidation of lipid acid. When lipid acid is oxidized, the chemical compound nonenal is produced, giving off the “old people smell” that many of us are familiar with.

Exactly why this happens is still a mystery. The cause of the musty smell in grandma’s house may actually be a grandma. Let’s go to grandpa’s room and see if it still smells funny. What causes ‘old person’ smell?”

Sure, these lines from “Rugrats,” an animated series that aired on Nickelodeon in the 1990s, were meant to be funny. But they also may have a basis in real life, relating to the widely held notion that the elderly emit a particular — and easily recognizable — body odor.

While the smell has been described as stale, medicinal, musty or simply “old person,” the Japanese have developed a more elegant term: kareishu. In one study, Japanese researchers traced the odor to a chemical compound called 2-nonenal.

The compound is a byproduct of other chemical breakdowns and emits a “greasy” or “grassy” odor as the molecules exit the skin and are released into the air. Researchers discovered that 2-nonenal was the only odor compound whose presence became stronger with age.

In the study, in which 22 people aged between 26 and 75 were asked to wear odor-collecting shirts to bed, researchers analyzed molecules that stuck to the cloth. The amount of 2-nonenal was three times as prevalent in the oldest subjects as it was in the middle-aged group. The youngest members of the study produced the least amount of 2-nonenal.

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Researchers speculate the increase in 2-nonenal may have to do with the breakdown of omega-7 unsaturated fatty acids, because these molecules were also present in the shirts worn by the study’s oldest subjects. It’s possible 2-nonenal may be produced as a byproduct of omega-7 as the compound deteriorates, possibly because of changes in metabolism as the body ages or changes in the amount of other chemicals that are released through the skin

Another study measuring participants’ abilities to identify the age of people by sniffing their sweat samples found that it was nearly impossible to discern the differences in odor between the 20- to 30-year-old group and the 45- to 55-year-old age group. Participants could, however, easily identify the scent of old people (75- to 95-year-olds). Even so, the participants didn’t rate the “old person” smell as particularly intense or unpleasant. It was simply uniquely recognizable.

Although the biological purpose behind “old person” smell is still unclear, some researchers believe it’s connected to a built-in age-detecting feature possessed by humans and animals. For instance, some animals can distinguish between older and younger animals by smell alone, and some animals are driven to mate with older animals.

It’s possible the ability to sniff out the smell of older animals meant that long-term survivors were revealed — and these survivors had a genetic advantage that boosted their odds of survival and reproduction. In essence, the scent we’ve come to call “old person” smell could be an advertisement for superior genetic quality. It gives a whole new meaning to the term “silver fox”.

While 2-nonenal is likely responsible for how body odor changes with age, it’s still unclear why this change happens. But experts believe evolution is part of the picture.

Remember, it isn’t just older adults who have a distinct smell. Infants, teenagers, young adults, and middle-aged adults each tend to have slightly different body odors. Experts believe these specific scents help keep the human species alive and well.

For example, that fresh baby smell may be more appealing to mothers, which helps with bonding. In adults, body odor may help signal someone’s fertility or health to find an optimal mate.

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Since the discovery of 2-noneal, several companies have started developing personal care products designed to mask the scent of older people, particularly in Japan. But there’s no evidence that these products do anything to target 2-nonenal.

Plus, there’s evidence that people generally don’t mind the smell associated with older people. In fact, that 2012 study found that participants rated the odors of older individuals as less unpleasant and less intense than the odors of some younger groups.

For the study, 44 men and women were divided into three different age categories: 20 to 30, 45 to 55, and 75 to 90. They were asked to sleep in a shirt specially fitted with underarm pads that could absorb odor for five consecutive days.

Participants were also asked to avoid foods that could interfere with their urine’s natural smell while on the sleep test. These included foods containing a lot of spices.

At the end of the five days, the underarm pads were collected and cut into quarters. Each piece was placed in a glass jar. The study’s authors asked individuals to smell the jar and guess the person’s age and sex.

The testers had a hard time detecting differences in scent between young and middle-aged people — they smelled too similar. They had a much easier time identifying samples from the study’s oldest group.

These results suggest that older people do have a very distinct smell, but it’s not necessarily unpleasant or intense.

If you’re concerned about age-related changes in your body odor, you don’t need to purchase any products specially formulated to target 2-noneal. Any scented product you enjoy will help mask the smell.

Alternatively, consider wearing your new scent as a badge of honor. Chances are, most people won’t even notice. And if they do, they likely won’t have any problem with it.

Body odor naturally changes as you age. For older people, this change in smell is likely due to an increase in levels of a compound called 2-nonenal.

No matter the cause, there’s no reason to run from these changes. Research suggests that, while people recognize older adults as smelling different, they don’t necessarily consider it an unpleasant smell.