---
title: The Science of Nonenal & Persimmon Tannin | Kiyo Clinical
canonical: https://kiyoclinical.com/pages/science
---

# Why your soap stopped working around 40

> It's not you — it's nonenal. Here's what changes in your skin chemistry with age, why regular soap can't wash it away, and how persimmon tannin does.

## Nonenal, in three steps

### 01 — Nonenal forms on the skin

From around age 40, shifting hormone levels cause skin lipids to oxidize into 2-nonenal — a fatty odor compound with a persistent, greasy-grassy smell. Production increases with age, regardless of hygiene.

### 02 — Regular soap washes around it

Nonenal isn't water-soluble and binds to skin and fabric. Ordinary cleansers lift away sweat and bacteria but leave nonenal behind — and deodorants only layer fragrance on top of it.

### 03 — Persimmon tannin breaks it down

Tannin from Japanese persimmon (*Diospyros kaki*) chemically binds to nonenal and neutralizes it on contact — a method used in Japanese bathing culture for centuries, now delivered in a daily bar.

## Inside the bar

- Persimmon extract — targets nonenal at the source
- Coconut & olive oil — cleanse while maintaining moisture
- Glycerin, sorbitol & sucrose — skin-comforting cleanse
- No synthetic fragrance, no added dyes, cruelty-free, quality-tested

## Next

- [Shop Persimmon Deodorizing Soap](https://kiyoclinical.com/products/persimmon-odor-defense-bar)
- [What is nonenal?](https://kiyoclinical.com/pages/what-is-nonenal)