Ask a Scientist: What Causes Old-People Smell?

The Scientist: Charlene Brannon, Ph.D., former professor of food chemistry at the University of Washington and scientific advisor at Mirai Clinical

The Answer: As we age, there are a lot of changes in our skin that we can see: wrinkles, sagging, dryness, etcetera and so on. There are also changes in our skin that might not be visible to the eye, but the nose surely knows. A 2001 study conducted by skincare scientists in Japan found that beginning around age 40, a person’s body odor contains a higher concentration of 2-Nonenal, a compound that has an unpleasant, greasy, grassy odor that we affectionately call “old-people smell.”

Sebaceous glands in skin release sebum, an oily combination of lipids that helps retain moisture. The sebum produced is broken down by bacteria on the surface of the skin, which contributes to body odor and can be exacerbated by hormonal changes and stress. In younger people, skin’s natural antioxidant defenses work to prevent these fatty acid breakdown products from being oxidized by the air and turned into other chemicals. Older skin has fewer antioxidants. That, coupled with hormonal shifts that increase lipid production by sebaceous glands, means that more of those free fatty acids will undergo oxidation. The results is an accumulation of oxidized substances including the particularly odiferous nonenal.

Because they’re not water soluble, the lipids that give rise to nonenal don’t wash off easily with regular soap. The company that Dr. Brannon works for, a Japanese skincare brand called Mirai, makes a body wash that specifically targets nonenal with persimmon extract. The tannins in the extract absorb up to 97 percent of the compound on the skin, according to Mirai’s clinical trials.The older we get, the more nonenal we produce. And, because nonenal is a small, volatile compound, it can be found in the air around skin, and absorbed into clothing, pillows and sofa cushions. All the while, our sense of smell deteriorates, making us less aware that it’s happening. So if someone gives you a gift certificate to Mirai for your birthday, take the hint.

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