Why do I still smell musty after a shower? The overlooked cause after 40

This is one of the most uncomfortable searches people make, and one of the most common. You wash every day, you use deodorant, and yet a faint musty, greasy or "old" smell is there on your collar, your pillow, or when you pull a shirt over your head. Someone close to you may have mentioned it. Here is what is usually going on, and it is not a hygiene failure.

Sweat odour and musty odour are different things

Ordinary body odour comes from bacteria breaking down sweat, mainly under the arms. It is sharp and sour, it is worse after exercise, and soap plus deodorant handles it. A musty odour that is still present after washing behaves differently: it is faint but persistent, it sits on the neck, behind the ears, the chest, the back and the scalp rather than the armpits, and it clings to fabric.

The usual cause: nonenal

From roughly age 40, the skin produces more of a fatty acid called palmitoleic acid. When it meets oxygen it breaks down into 2-nonenal, an oily compound with a musty, greasy, slightly waxy smell. Japanese researchers identified it in 2001 and it has a name in Japan, kareishu. Two properties make it stubborn:

• It is not water-soluble and not produced by bacteria, so antibacterial soap and ordinary washing leave most of it behind.
• It is oily, so it soaks into pillowcases, collars, hats and the headrest of your car and re-deposits onto clean skin.

Read the full nonenal explainer for the science.

A quick way to check

1. Smell your pillowcase in the morning, before you shower. A musty note there points to nonenal.
2. Ask someone you trust to smell the back of your neck after your normal shower. If it is still there, ordinary soap is not reaching it.
3. Note where the smell is. Armpits: sweat odour. Neck, ears, chest, back, scalp: nonenal.

Other causes worth ruling out

Damp towels and washing machines that need a hot cycle can leave a mildew smell on clothes that gets mistaken for body odour. Certain medications and diets can change body odour. Persistent unusual body odour with other symptoms should be discussed with a doctor. But for most people over 40 with a musty smell that survives the shower and follows them to the pillow, nonenal is the answer.

What can help wash it away

Persimmon (kaki) tannin is traditionally used to help rinse nonenal away with water. That is the reason persimmon soap exists, and persimmon tannin has been used in Japan for generations. Use it daily on the places the smell sits, leave the lather for a minute, and rinse. KAKIORA is a Japanese persimmon soap made for exactly this, with a gentle, soap-free base of coconut-derived cleansers, glycerin and skin-softening emollients so that daily use suits older skin. See best soap for body odour for how it compares with other types.

Fix the fabric too

Because nonenal re-deposits from fabric, the smell will not fully go until the bedding and collars are dealt with. Wash pillowcases and shirt collars hot, air the mattress and pillows, and change pillowcases every two or three days for the first fortnight. Shower in the evening so you go to bed with clean skin. Our guide to getting rid of old person smell gives the full routine.

How long it takes

Everyone's skin is different, but many people notice a fresher feel within the first week of daily persimmon soap, and it can keep improving over a month as the fabric around them stops re-depositing the compound. If nothing changes after four weeks, nonenal was probably not your issue, which is why KAKIORA offers a 60-day money-back promise.