Scientists Say This "Old Person Smell" Isn't Caused By Poor Hygiene — And Regular Soap May Not Be Enough

By Health & Wellness Desk · Updated June 2026 · 4 min read

Researchers have identified a compound called 2-Nonenal that naturally increases with age and can create a musty body odor which lingers on skin and fabric — even after a thorough shower.

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What Is "Old Person Smell"?

Most people first notice it as a faint, unfamiliar odor that seems to appear out of nowhere after around age 40. It isn't the result of skipping a shower or wearing the same shirt twice — and that's exactly what makes it so frustrating. You can do everything right and still catch a trace of it on a collar, a pillow, or a favourite jacket.

The reason it feels so persistent is that it doesn't just sit in the air. It clings.

It can cling to:

Shirts

Bedding

Jackets

Towels

Skin

The smell is often described as:

Musty

Oily

Stale

Dusty

Researchers believe a naturally occurring compound called 2-Nonenal is largely responsible. It forms as the skin's natural oils oxidise with age, and because it's oily by nature, it bonds to skin and fabric and resists ordinary washing.

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Why Traditional Soaps Often Fall Short

The problem isn't that people aren't washing. It's that most soaps were never designed for this kind of odor in the first place.

Most soaps are designed to remove:

Dirt

Sweat

Surface bacteria

But age-related odor compounds like 2-Nonenal bind to the skin's natural oils and remain on the skin long after washing. A standard bar lifts the obvious grime and rinses away — while the compound responsible for the smell stays exactly where it was.

This is why so many people still notice odor returning shortly after a shower, and assume they simply need to wash harder or more often.

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Japan's Secret For Age-Related Odor

In Japan, age-related body odor is common enough to have its own name: Kareishu. And rather than trying to mask it, Japanese skincare took a different approach decades ago — targeting the compound itself.

For years, Japanese skincare experts have relied on one ingredient:

Persimmon Extract

Persimmon contains powerful natural tannins that help neutralise odor-causing compounds rather than simply masking them with fragrance. It's a fundamentally different idea of "clean" — one that works with the skin's chemistry instead of perfuming over the top of it.

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Introducing

SAP Skin Persimmon Soap

A Traditional Japanese-Inspired Soap Designed To Help Remove Age-Related Odors

Unlike ordinary soaps that simply leave behind fragrance, SAP Skin Persimmon Soap combines gentle cleansing ingredients with persimmon extract to help target the source of stubborn odors — not just cover it for an hour or two.

It's made to fit the shower you already take: a rich, creamy lather, a clean natural finish, and a single bar the whole household can share.

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How Persimmon Soap Works Differently

The difference comes down to chemistry rather than scent. Persimmon is rich in a polyphenol called shibuol — a natural tannin that binds to odor compounds on the skin's surface and helps neutralise them, instead of layering perfume over the top.

Paired with a gentle, skin-conditioning cleansing base, the bar lifts away the day's sweat and oil without leaving skin tight or stripped — so you're left genuinely fresh rather than freshly fragranced.

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Benefits:

Real persimmon extract

Natural tannins work to neutralise odor compounds at the source.

Rich, creamy lather

A little goes a long way, spreading easily across the whole body.

Helps remove odor-causing buildup

Targets the compounds ordinary soap tends to leave behind.

Leaves skin feeling clean and refreshed

A light, natural finish that lasts through the day.

Suitable for daily use

Gentle enough to use every day, on the whole family.

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How To Use

Lather

Wet the bar and work up a rich lather between your hands or on a washcloth.

Massage

Spread across the whole body, focusing on the chest, back, and underarms.

Rinse

Rinse thoroughly and pat dry. Use daily — clothing and bedding feel the difference too.

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SAP Persimmon Soap vs Ordinary Soap

What matters

SAP Persimmon Soap

Ordinary Soap Bar

Targets 2-Nonenal odor

Yes — persimmon tannins

Mostly surface cleaning

Lather & coverage

Rich, creamy

Varies, can dry skin

Daily-use comfort

Gentle, conditioning

Can leave skin tight

Approach to odor

Neutralises at source

Masks with fragrance

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Who Is It For?

If you've noticed any of the following, this soap may help:

A lingering musty odor you can't quite wash away

Bedding that smells stale more quickly than it used to

Clothes that retain an odor even after washing

Reduced confidence around friends, family, or colleagues

This soap may help.

Feel Cleaner. Smell Fresher. Regain Confidence.

Try SAP Skin Persimmon Soap today and discover why thousands are switching from ordinary soaps.

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Persimmon Extract

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