Short answer: Nobody has shown that persimmon soap works better than ordinary soap. Laboratory studies suggest compounds from persimmon can capture some smelly gases. The only human soap study we found, a small Japanese trial of a bar containing persimmon and tea extracts, measured less nonenal after four weeks, but it had no comparison group. What is certain is that washing with any soap helps wash away the oily residue that carries the smell.
If a packet says a soap tackles "older person smell", it is fair to ask whether that has been proven, especially before you spend money on it. This article sets out what has been studied, how strong that evidence is and what is still unknown. It ends with a simple way to judge for yourself whether a persimmon soap makes any difference for you.
What persimmon soap is supposed to do
Persimmon soap contains extract of the Japanese persimmon, Diospyros kaki, often made from the unripe, astringent fruit. Unripe persimmons are rich in tannins, the plant compounds behind that dry, puckering feeling in your mouth if you bite one too early.
The idea behind persimmon soap has two parts:
- Soap lifts skin oil and dirt, and with them some of the smell.
- Persimmon tannins are said to bind smell molecules such as nonenal, so the soap does more than an ordinary bar.
The first part is true of every soap. The second part is the real question.
What is reasonably well established
- Nonenal exists, and in Japanese studies it increases with age. The original study found 2-nonenal only in participants aged 40 and over (Haze et al., 2001, Journal of Investigative Dermatology). Our guide what is nonenal? explains how it forms.
- Not everyone has measurable amounts. A US study of 25 adults did not detect 2-nonenal at all (Gallagher et al., 2008, British Journal of Dermatology).
- Washing helps with body odour. Regular washing and clean clothes are the first self-help steps on the NHS body odour page. That applies to any soap.
What laboratory and animal research shows
These are the persimmon studies we read in full or in abstract. None of them tests a soap on human skin.
- Gases in the lab. Researchers at Huazhong Agricultural University in China extracted persimmon polyphenols with so-called natural deep eutectic solvents and found the mixtures could capture ammonia and hydrogen sulphide, the rotten-egg gas (Li et al., 2026, Foods). This was chemistry in a laboratory, not skin, and it did not look at nonenal.
- Mouth bacteria and dogs. In the lab, persimmon tannin killed a mouth bacterium linked to gum problems in dogs and cut the smelly sulphur gas it produces. Dogs given a persimmon tannin gel for a month had lower levels of two sulphur gases in their breath, although their gum and plaque scores did not change significantly (Toyooka et al., 2025, Journal of Pharmacological Sciences).
- Eating persimmon extract. In a small Japanese trial, 11 adults ate garlic soup. After a single dose of persimmon extract, their breath contained less of one sulphur compound, dimethyl sulphide (Hamadate et al., 2014, Japanese Journal of Complementary and Alternative Medicine). That is about food, not soap.
Together, these make it plausible that persimmon compounds react with some smell molecules. But this is limited evidence from the lab, from animals and from the mouth. It tells us little about what a soap does in the minute or so it spends on your skin.
The one human soap study we found
One study tested a soap containing persimmon extract on people and measured nonenal: Tatsuguchi et al., 2012, Journal of Japan Association on Odor Environment 43(5): 362–366. We read the full paper.
- Who: 20 Japanese men aged 43 to 75, who were bothered by age-related body odour or had been told they had it.
- What: for four weeks they washed their whole body daily with a bar containing a blend of four plant extracts (oolong tea, sweet tea, green tea and persimmon tannin), plus an antibacterial agent, charcoal and mud.
- What was measured: nonenal in a cotton T-shirt slept in for three nights before each check; odour strength at the back of the neck and the armpits, judged by one certified odour assessor; and the men's own ratings.
- Results: all three measures were significantly lower at two and four weeks than at the start. Reading from the paper's chart, nonenal in the T-shirts was roughly 40% lower after four weeks.
That sounds encouraging, but the limits matter:
- No comparison group. Nobody used an ordinary soap for comparison. The authors say so themselves and note that a placebo effect may have influenced the men's own ratings, which had already improved after a single day.
- A mixture. Persimmon was one of four plant extracts, alongside an antibacterial agent, charcoal and mud. It is impossible to say which ingredient did what.
- A commercial interest. The study came from the research institute of the company that developed the extract blend.
- Small and narrow. Twenty men, all Japanese, and no women.
How strong is the evidence?
| Study | What was tested | Type of evidence | What it tells us about persimmon soap |
|---|---|---|---|
| Li et al., 2026 | Persimmon polyphenols and smelly gases | Laboratory | Little: no skin, no nonenal |
| Toyooka et al., 2025 | Persimmon tannin and mouth bacteria | Laboratory and dogs | Little: mouth, not skin |
| Hamadate et al., 2014 | Eating persimmon extract | Small human trial | Little: food, not soap |
| Tatsuguchi et al., 2012 | Soap with persimmon, tea extracts and more | 20 men, before and after only | A hint, not proof |
What we still don't know
- Whether persimmon soap works better than ordinary soap. A search of PubMed on 11 October 2026 found no controlled study comparing the two.
- How much extract a soap needs, and whether a short wash leaves it on the skin long enough to matter.
- How results compare in women and in people outside Japan.
"Not proven" is not the same as "doesn't work". It means nobody can honestly sell it to you as proven, and you are entitled to try it with an open but sceptical mind.
How to judge the results for yourself
- Read the label. Look for Diospyros kaki or persimmon tannin in the ingredients. Some products only smell of persimmon.
- Change one thing at a time. Keep your laundry routine, clothes and bathing habits the same, so you know where any difference comes from.
- Allow four weeks. The Japanese study measured at two and four weeks.
- Try a T-shirt test. Sleep in a freshly washed cotton T-shirt for three nights, then smell it. Do this at the start and again after four weeks. It is a home version of what the researchers did.
- Ask an honest nose. We get used to our own smell, so a partner or close friend may notice a change before you do.
- Watch your skin. If it becomes dry, red or itchy, stop. If a rash doesn't settle, ask a pharmacist or your GP.
Our guide on how to use persimmon soap covers the areas worth focusing on. If you want to see the options side by side, our persimmon soap comparison lists several brands.
Frequently asked questions
Is persimmon soap better than ordinary soap?
We don't know. We found no study that compares persimmon soap directly with ordinary soap. Any soap helps wash away the oily residue that carries the smell.
Will persimmon soap get rid of nonenal completely?
No. No soap can do that, because your skin makes fresh oil every day. A regular routine matters more than any single wash.
How soon might I notice a difference?
Allow a few weeks. The only human soap study measured at two and four weeks. If you notice nothing after a month of fair testing, it is reasonable to spend your money elsewhere.
Why is persimmon linked with Japan?
Much nonenal research comes from Japan, and persimmon has a long history there. Fermented persimmon juice, kakishibu, has traditionally been used to protect wood and paper (Tokin et al., 2021, Biomolecules). Our article on kakishibu tells that story.