It’s that distinct scent. You’ve probably noticed it in a grandparent’s spare bedroom, a nursing home hallway, or even just hugging an aging relative. It isn't necessarily a bad smell—some find it comforting, almost like old books or dried grass—but it’s undeniably specific. For years, people just chalked it up to poor hygiene or stale air. That’s wrong. It’s biology.
Actually, it’s chemistry.
When we talk about why do older people smell, we aren't talking about sweat or a lack of showering. We’re talking about a very specific chemical compound called 2-nonenal. It’s an unsaturated aldehyde. It’s also completely unavoidable as we age.
The 2-Nonenal Discovery
Back in 2000, researchers at the Shiseido Research Center in Yokohama, Japan, decided to figure out what was actually going on. They didn't just guess. They used gas chromatography and mass spectrometry to analyze the body odors of people ranging from ages 26 to 75.
What they found changed the way we look at aging skin.
They identified 2-nonenal as the primary culprit. Interestingly, this compound was only detected in subjects over the age of 40. The older the participant, the higher the concentration of the chemical. Younger people simply didn't produce it. It wasn't a matter of them being "cleaner"; their bodies just weren't making the molecules yet.
How your skin changes after 40
Think about your skin as a factory. As you get older, the factory starts changing its output. Your skin’s natural antioxidant defenses begin to weaken. At the same time, the composition of your skin oils—specifically omega-7 unsaturated fatty acids—starts to shift.
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When these fatty acids are secreted by the sebaceous glands, they react with oxygen in the air. This process is called lipid peroxidation. Because the body’s antioxidant levels are lower in seniors, there’s nothing to stop this oxidation.
The result? 2-nonenal.
It’s greasy. It’s stubborn. And honestly, it’s incredibly hard to wash off. Because it is an oil-based byproduct, it doesn't dissolve in water. You can scrub with standard soap all day, but the 2-nonenal molecules often stay bonded to the skin or the fibers of clothing.
Beyond the Chemistry: Environmental Factors
While 2-nonenal is the "core" reason why do older people smell, it isn't the only factor. Context matters. Living environments play a massive role in how we perceive the scent of aging.
Older individuals often spend more time indoors. If windows aren't opened frequently, "old person smell" can permeate upholstery, carpets, and curtains. It’s a cumulative effect. You have the biological scent of the person mixing with the literal dust of a home that might not have been deep-cleaned in a decade.
Then there’s the medication.
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As we age, the list of prescriptions usually grows. Many drugs—especially those for blood pressure, diabetes, or depression—are metabolized by the body and excreted through sweat and skin. Sometimes these medications cause "dry mouth," which changes the microbiome of the mouth and leads to a distinct type of halitosis. It all blends together into one olfactory profile.
The hygiene misconception
It’s a bit of a tragedy that society associates this smell with neglect. In reality, an elderly person could be meticulously clean and still carry the scent of 2-nonenal.
In fact, over-showering can sometimes make it worse. Aging skin is thinner and drier. Using harsh soaps to "scrub away" the smell can cause micro-tears in the skin, leading to infections or dermatitis. This adds another layer of medicinal or "sickly" scents to the mix. It's a frustrating cycle.
Cultural Perceptions of the Scent
Interestingly, not everyone hates this smell. In Japan, there’s a specific term for it: kareishu.
While the West often views any body odor as a failure of hygiene, many eastern cultures view kareishu with a sense of nostalgia or respect. It’s seen as a sign of a life long-lived. Scientists have even found that when people are told a scent is "old person smell" versus "fresh spring rain," their brain reacts differently. The "gross" factor is often psychological.
A study published in PLOS ONE in 2012 by Johan Lundström found that humans can actually identify the age of a person just by smelling their body odor. Surprisingly, the participants in the study rated "old person smell" as less intense and less unpleasant than the body odor of middle-aged men.
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Middle-aged men, apparently, smell the worst. Who knew?
Can You Actually Get Rid of It?
If you're worried about why do older people smell because you're noticing it in yourself or a loved one, there are ways to manage it. But forget the "extra-strength" deodorant. That won't touch 2-nonenal.
Since the compound is oil-based, you need specific ingredients to break it down.
- Persimmon and Green Tea: In Japan, persimmon-based soaps are a huge industry. Persimmon extract contains tannins (specifically gallocatechins) that naturally break down 2-nonenal.
- Hydration: Drinking water helps dilute the fatty acids in your sebum.
- Air Circulation: Oxidized oils get trapped in fabrics. Keeping a home well-ventilated and washing clothes in hot water can prevent the scent from "settling" into the environment.
- Antioxidant-Rich Diet: While not a "cure," a diet high in antioxidants can theoretically slow down the lipid peroxidation process on the skin's surface.
It is also worth noting that sudden changes in body odor shouldn't be ignored. While 2-nonenal is a slow, natural build-up, a "fruity" smell can indicate ketoacidosis (diabetes), and a "musty" or "bleach-like" smell can sometimes point to liver or kidney issues.
The Reality of Aging
Ultimately, the scent of aging is just another biological milestone. Like grey hair or wrinkles, it is a marker of time. We spend billions of dollars trying to look younger; it’s only natural that we’ve developed a stigma against smelling older.
But the science is clear. It isn't "dirt." It isn't "gross." It is just a specific molecule, 2-nonenal, doing exactly what chemistry dictates it should do when skin oils meet oxygen.
Next Steps for Managing 2-Nonenal
- Switch to an oil-based cleanser: Since 2-nonenal isn't water-soluble, an oil-based cleanser or a soap containing persimmon extract is more effective at breaking down the molecules than standard bar soap.
- Focus on the "hot zones": The compound is most concentrated behind the ears, on the neck, and in the armpits. Focus cleansing efforts there.
- Update laundry habits: Use a laundry booster designed to break down body oils (like those containing enzymes or borax) when washing linens and undershirts.
- Consult a professional: if the odor is accompanied by significant skin changes or a "sweet/fruity" breath, schedule an appointment with a GP to rule out metabolic shifts like undiagnosed Type 2 diabetes.