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Mould on clothes I had put away. Can I get it off, and how do I stop it in the closet?

This answer is a draft. It stays unpublished until legal review and source verification are complete.

You open the closet after the rainy season (tsuyu, June to mid-July) and find white specks on a black jacket, or green fuzz on a leather bag. Japan's hot, humid summer is ideal for mould on clothing, and every year it strikes the clothes people "had not taken out for a while". Here is how to remove it, and separately, how to stop it at the root.

Types of mould and how to remove them

• Conditions for mould: humidity above 60%, temperature 20–30°C, and food (skin oil, dust, food traces). A Japanese oshiire (built-in closet) between June and September can reach 70–80% humidity. Of the three conditions, cutting off humidity and food is the core of prevention.
• Handling with care: do the brushing outdoors and wear a mask, so you do not breathe in the spores. Brushing indoors sends spores into the air and onto other clothes. Chlorine bleach is for whites only — never on colours, prints, wool or silk — and mixed with an acidic cleaner it gives off toxic gas.
• Keeping closet humidity below 60%:

- Dehumidifier packs (除湿剤, joshitsuzai; place the calcium-chloride type low down and replace when the water has collected) - A fan or air circulator: open the doors and blow air through for 30 minutes a few times a month - Fill no more than 80%: a finger's width between garments - Keep things at least 10 cm off the floor; moisture collects near the floor - Lay a slatted board (すのこ, sunoko, sold at home centres) underneath and keep 5 cm from the wall

• Never put worn clothes away unwashed: skin oil and moisture are exactly the food and water mould needs. Remove the plastic from dry-cleaned clothes too before storing (it traps moisture).
• If the musty smell will not go: the mould may be gone but the smell remains. Sun-drying, a soak in baking-soda water (重曹, jūsō) or steaming can improve it. If not, take it to a cleaner and tell them it is mould.

[Verify] The conditions for mould growth (humidity, temperature) are general figures based on municipal public-health documents. The warning against mixing bleaches follows NITE and makers' labels.

Misunderstanding 1｜Drying in the sun kills the mould

UV reduces the mould on the surface, but the hyphae inside the fibres remain. White mould needs brushing and wiping; black mould needs a bleach soak. Sun-drying is the finishing step.

Misunderstanding 2｜I can just brush it off indoors

The spores fly and spread to other clothes and the room. Do it outside or on the balcony, wearing a mask.

Misunderstanding 3｜Chlorine bleach will shift it in one go

It strips colour from prints, and dissolves wool and silk. Use oxygen bleach for black mould on clothes. Chlorine is for white cotton only, and never mixed with other cleaners.

Misunderstanding 4｜With a dehumidifier pack in the closet, mould cannot grow

A dehumidifier pack is only a helper in a small space; it cannot keep up with overfilling, no airflow and unwashed clothes. Use all four measures together.

Misunderstanding 5｜Leaving the dry-cleaner's plastic on keeps clothes clean in storage

The plastic traps moisture and causes mould and discolouration. Take it off when you get home and switch to a non-woven cover.

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Sources

• Tokyo Metropolitan Government Bureau of Public Health (東京都保健医療局), "Measures against mould: preventing mould in the home"

https://www.hokeniryo.metro.tokyo.lg.jp/

• National Institute of Technology and Evaluation (NITE, 独立行政法人製品評価技術基盤機構), "Accidents from mixing chlorine bleach with acidic products"

https://www.nite.go.jp/jiko/chuikanki/

• Japan Soap and Detergent Association (日本石鹸洗剤工業会), "Correct use of bleach"

https://jsda.org/w/03_shiki/

⚠️ 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.

Follow the care label and the maker's instructions for any garment, shoe or bag. For expensive or sentimental items, ask a specialist cleaner or repairer.

Sources

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