Body odour and "ageing odour": how should I wash, and can over-washing backfire?
This answer is a draft. It stays unpublished until legal review and source verification are complete.
"Kareishū" (加齢臭, ageing odour) is a term that spread in Japan around 2000, after a sebum component called nonenal, which increases from the 40s onwards, was identified as the substance responsible. You will see it on drugstore shelves and hear it in conversation. Sweat odour, armpit odour (wakiga), ageing odour, "middle-age greasy odour" — each has a different cause, and the way to wash is different too.
Types of odour and what causes them
| Type | Typical age | Substance | Where it forms | What to do |
|---|---|---|---|---|
| Sweat odour | All ages | Eccrine sweat (almost all water) broken down by skin bacteria into short-chain fatty acids and so on | Whole body, feet | Wipe often, change clothes, breathable fabrics |
| Wakiga (axillary osmidrosis) | Puberty onwards | Apocrine sweat (containing fats and proteins) broken down by bacteria. Hereditary constitution (about 10–15% of Japanese people) | Armpits, around the nipples, groin | Antiperspirant (aluminium chloride etc.), removing armpit hair, dermatology or plastic-surgery clinic |
| "Middle-age greasy odour" (ミドル脂臭) | Mid-30s to 50s | Diacetyl (lactic acid in sweat broken down by bacteria) plus sebum. Smells like old cooking oil | Back of the head, nape | Wash the scalp, change the pillowcase |
| Ageing odour (加齢臭) | 50s onwards | Nonenal (fatty acids in sebum oxidised and broken down). Smells like old books or candles | Chest, centre of the back, behind the ears, neck | Limit sebum oxidation (lifestyle), wash those areas |
| Fatigue odour (疲労臭) | All ages | Ammonia (the liver cannot keep up) | Whole body | Sleep, rest, less alcohol |
- How to wash: lather soap or body wash and use your hands or a cotton towel. Scrubbing with a nylon towel (ナイロンタオル, the rough wash towels sold in every Japanese supermarket) strips the stratum corneum, sebum is over-produced, and the odour can get worse. Left-over soap (behind the ears, back of the neck, back) causes odour. Once a day is enough; after sweating, a rinse in the shower is fine.
- Head: for both middle-age odour and ageing odour, the scalp is a common source. Rinse first → wash the scalp with your fingertips → rinse well → dry straight away (sleeping with wet hair lets bacteria multiply).
- Clothes and bedding: much of the odour is oxidised sebum stuck to clothing. Underwear and pillowcases daily; soak yellowed collars and underarms in oxygen bleach (酸素系漂白剤, sanso-kei hyōhakuzai) at 40°C (104°F). The musty smell of laundry dried indoors is a different bacterium (Moraxella) and needs a clothing-side fix (see our separate article).
- Diet and lifestyle: too much fat and animal protein, alcohol, smoking, lack of sleep and stress push sebum oxidation and ammonia odour up. Vegetables and fruit (antioxidants) and moderate exercise (keeps sweat glands working) push the other way.
- Antiperspirants and deodorants: a combination of an antiperspirant (sweat-suppressing) ingredient and an antibacterial ingredient. Apply to clean, dry skin (see our separate article on antiperspirants).
- Hard to judge on yourself: you get used to your own smell, so people ask family or put a worn undershirt in a bag and smell it a few hours later.
- When to see a doctor: wakiga that interferes with daily life (surgery is available under health insurance); a sudden strong ammonia or sweet smell (possible liver disease, diabetes or other illness).
[Verify] The proportion of Japanese people with wakiga and the explanations of nonenal and diacetyl are general descriptions based on research announcements by cosmetics makers. Check against material from the Japanese Dermatological Association and related societies.
Misunderstanding 1｜I worry about smell, so I scrub hard with a nylon towel
It strips the stratum corneum, increases sebum, and can make things worse. Lather and hands, gently, and rinse thoroughly.
Misunderstanding 2｜Everyone gets ageing odour equally as they get older
How much sebum oxidises differs with lifestyle. Fat, alcohol, sleep and exercise leave room for change.
Misunderstanding 3｜Sweat itself smells
Sweat is almost odourless; the smell appears when skin bacteria break it down. Wiping, washing and drying to limit the bacteria is the answer.
Misunderstanding 4｜Perfume or a body spray is enough to mask it
If you do not deal with the source (sebum, bacteria, clothing), the smells can mix into something more unpleasant. Washing and clothing come first.
Misunderstanding 5｜Wakiga means someone is unclean
Wakiga is a constitution — the number of apocrine sweat glands — and has nothing to do with cleanliness. If antiperspirant is not enough, you can consult a dermatology or plastic-surgery clinic (some procedures are covered by health insurance).
---
Sources
- Japanese Dermatological Association, "Dermatology Q&A: axillary osmidrosis (wakiga) and hyperhidrosis" [皮膚科Q&A：腋臭症（わきが）・多汗症]
https://www.dermatol.or.jp/qa/
- Japanese Dermatological Association, "Guidelines for primary focal hyperhidrosis, 2023 revision" [原発性局所多汗症診療ガイドライン 2023年改訂版]
https://www.dermatol.or.jp/uploads/uploads/files/guideline/
- Japan Cosmetic Industry Association, "Using cosmetics correctly: antiperspirant and deodorant products" [化粧品の正しい使い方：制汗・デオドラント製品]
https://www.jcia.org/user/public/knowledge/usage
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
About this article
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.
Cosmetics are not medicines and are not meant to diagnose, heal or prevent any condition. If your skin reacts, stop using the product and see a dermatologist.
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