KAKIORA Japanese persimmon soap bars with a fresh persimmon

Nonenal: the "older person smell" explained, and how to wash it away

You may never have typed “nonenal”. In the US, this smell is more often looked up as “old person smell” or “old man smell”, sometimes on behalf of a parent. This guide names the compound behind it, explains why a regular shower leaves it behind and sets out a simple daily routine. Below the article, we add what a US research team found when it went looking for nonenal, and when a doctor visit makes sense.

Most people notice it on someone else before they notice it on themselves: a faint, slightly waxy, "old book" kind of smell that hangs around even after a shower. It has a name, nonenal, and it is one of the most common and least talked about changes that come with getting older. This guide explains what it is, why an ordinary bar of soap does so little about it, and what actually helps.

What is nonenal?

Nonenal (2-nonenal) is a naturally occurring compound that forms on the skin when certain fatty acids in skin oil, mainly omega-7 acids such as palmitoleic acid, are broken down by oxygen. Japanese researchers first described it in 2001, which is why so much of what we know about it, and so many of the products designed around it, come from Japan.

From roughly the age of 40 the skin produces more of these fatty acids while its natural antioxidant defenses slow down. The result is more nonenal on the skin's surface. It is not a sign of poor hygiene. People who shower every day still produce it.

What does it smell like?

People describe it as greasy, grassy, slightly musty or like old paper or candle wax. It is mild rather than sharp, which is exactly why it is easy to miss on yourself: the nose tunes out familiar smells, and this one builds up slowly. It tends to sit on the skin around the chest, back, neck and behind the ears, and it transfers easily to collars, pillowcases and bedding.

What the research actually shows

The term comes from a 2001 study by researchers at Shiseido, published in the Journal of Investigative Dermatology (Haze et al., 2001). They studied the body smell of people aged 26 to 75 and found three things:

  • 2-nonenal, which they describe as having an "unpleasant greasy and grassy" smell, was detected only in participants aged 40 or older.
  • Omega-7 unsaturated fatty acids and lipid peroxides on the skin surface also increased with age, and the amount of 2-nonenal rose with them.
  • In lab tests, 2-nonenal formed only when omega-7 fatty acids were broken down by oxidation.

What it does not show: this is one study. It does not prove that everyone over 40 has a noticeable smell, and it did not test any soap or treatment.

In plain terms, nonenal is not a sign of poor hygiene. It forms on the skin as natural skin oils oxidize, which is why washing well every day, and laundering clothes and bedding often, makes a difference.

Why ordinary soap does not shift it

Nonenal is not water soluble. It sits inside the oily film on the skin, so a quick rinse or a light lather washes off the fresh sweat on top and leaves the oily layer, and the smell, behind. Strong deodorants and perfumes cover it for a few hours, and stripping soaps can make skin dry and tight without dealing with the cause.

What is needed is a wash that lifts the oily residue itself, gently enough to use every day.

Why persimmon?

Japanese persimmon (kaki) is rich in tannins, natural plant compounds that are thought to bind to odor-carrying molecules and help wash them away with the water. Persimmon tannin has been used in Japan for centuries, on everything from paper to fabric, and it is traditionally valued for tackling smells rather than masking them. In a modern soap it is designed to do two useful things at once: help break down the oily film where nonenal sits, and help carry the odor molecules off the skin.

Our KAKIORA Japanese persimmon soap pairs persimmon extract with a gentle, soap-free base of coconut-derived cleansers, glycerin and skin-softening emollients, so it cleans the residue away without leaving mature skin feeling stripped.

A simple daily routine that works

  1. Wash the right places. Chest, back, the back of the neck, behind the ears and under the arms. Lather with your hands or a soft cloth and give it 20 to 30 seconds before rinsing.
  2. Use it daily. Nonenal forms continuously, so results come from routine rather than an occasional deep clean. Many people notice a fresher feel within the first few days, though everyone's skin is different.
  3. Change what touches your skin. Pillowcases twice a week, fresh collars, and air bedding in the morning. Nonenal builds up in fabric.
  4. Look after the skin barrier. Dry, over-washed skin produces more oil. A gentle, moisturizing wash beats a harsh one.
  5. Everyday basics help too. Good sleep, less alcohol and plenty of water all reduce how much oxidized oil ends up on the skin.

Is it a health problem?

No. Nonenal is a normal part of skin chemistry and is not a disease or a sign of one. If you notice a sudden change in body odor that is very different from this, that is worth mentioning to a doctor, but the everyday "older skin" smell is simply something to wash properly.

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Frequently asked questions

Does nonenal affect men and women equally? Yes. It increases with age in both. Men often notice it earlier because they tend to produce more skin oil.

How long does a bar of KAKIORA last? Used once a day on the odor-prone areas, one bar lasts around two weeks.

Can I use it on my face? It is a gentle bar, but we designed it for the body. If you use it on your face, avoid the eye area and follow with your usual moisturizer.

Ready to try it? Choose your KAKIORA pack. Every order is covered by our 60-day money-back promise.

What US research adds to the nonenal story

The best-known nonenal paper is Japanese, but a notable follow-up took place in the United States. A team at Philadelphia’s Monell Chemical Senses Center sampled skin odor from 25 healthy volunteers between 19 and 79 years old, at two sites: the upper back and the forearm (Gallagher et al., 2008, British Journal of Dermatology). No technique they tried picked up 2-nonenal. What did rise with age was a set of other compounds, among them nonanal, a near chemical cousin. The team raised the possibility that eating habits, for instance a diet rich in fish and seafood, partly account for the Japanese findings.

A later Monell project gave 41 young adults body odor samples from three age groups to rate. The volunteers could reliably link only the samples from people aged 75 to 95 to the right age group, and they scored those samples as milder and less unpleasant than odor collected from younger and middle-aged adults (Mitro et al., 2012, PLoS One).

What that means if you live in the US

  • Nonenal is a credible piece of age-related odor rather than the full explanation, so a routine covering skin, clothing and bedding beats any single product.
  • An older person’s scent can be recognizable without being stronger. Smelling “older” and smelling unpleasant are not the same thing.
  • Fabric holds on to the residue, too. Our guide to nonenal in clothes, sheets and pillows covers that side.

When it is a question for your doctor

A slow, mild shift over years is typical of aging skin. Book a visit with your primary care doctor if your body odor changes suddenly, or if it smells fruity, fishy, or like ammonia or bleach. The American Academy of Dermatology’s website, which we read on October 12, 2026, also notes that unusual or strong body odor has many possible causes and that a board-certified dermatologist can look into the skin-related ones.

If you decide to try a persimmon bar, KAKIORA ships from the UK to US addresses for a flat $3 on one-time orders. To see how a nonenal soap differs from an everyday bar, read our nonenal soap explainer.

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