The actual cause has a name. A compound called 2-nonenal forms when fatty acids on mature skin break down through oxidation. The process speeds up in your forties and fifties. 2-nonenal is oil-based, which is why it outlasts a standard wash. It is not a hygiene issue. It is a skin chemistry issue, and it needs a different kind of answer.
That answer, it turns out, has existed in Japan for centuries.
Persimmon has been used in traditional Japanese cleansing preparations for generations. The reason is its tannin content. Natural persimmon tannins bond directly to 2-nonenal molecules and break them down, rather than masking them with fragrance. Japanese women have understood this for a very long time. The rest of the world is only now catching up.
That is what led me to Zaymi. A Japanese persimmon soap made specifically for this problem. One bar, made with persimmon extract, cold-pressed olive oil, and coconut oil. No synthetic fragrance, no harsh sulfates, nothing that does not belong there.