What are the common misunderstandings about cutting nails and ingrown toenails?
This answer is a draft. It stays unpublished until legal review and source verification are complete.
Few people are ever taught how to cut their nails, and "short and rounded" is taken for granted worldwide. Yet that is one of the main causes of pincer nails and ingrown toenails. The Japanese Dermatological Association and the Japanese Society for Foot Care and Podiatric Medicine recommend the "square-off" cut instead.
How to cut
| Item | Toenails | Fingernails |
|---|---|---|
| Shape | Square-off: cut straight across and round only the corners slightly with a file | Rounding is fine, but do not cut too short |
| Length | Level with the toe tip or slightly longer (0–1 mm) | Slightly shorter than the fingertip |
| Timing | After a bath (nails are soft) | Same |
| Tools | Straight-edged clippers or nail nippers. Cut in several small snips, not one | Nail clippers |
| Filing | In one direction, not back and forth | Same |
| Frequency | About once a month (toenails grow at half the speed of fingernails) | Once a week |
| Cuticles | Do not force them off. Push back gently at most | Same |
| Problem | What it is | What to do |
|---|---|---|
| Ingrown nail (陥入爪) | The corner of the nail digs into the skin: redness, pain, pus | Stop cutting short; switch to square-off. For pain or pus, see a dermatology or plastic-surgery clinic (taping, wire correction, surgery) |
| Pincer nail (巻き爪) | The nail curls sideways. Cutting too short, ill-fitting shoes, ageing, the way you walk | Shoe size (see our article on wearing shoes); correction (often not covered by health insurance) |
| Nail fungus (爪白癬, onychomycosis) | Thick, cloudy white to yellow, brittle | Dermatology clinic (oral or topical medicine over several months) |
| Nails in older people | Thick and hard, cannot cut them yourself | Foot care (nursing, care services), dermatology clinic |
- The Japanese Dermatological Association and the Japanese Society for Foot Care and Podiatric Medicine explain that the main causes of ingrown nails are cutting too short and shoes, and that prevention is the square-off cut.
- People with diabetes risk infection and tissue death from small wounds on the feet; cut nails with care, and professional foot care at a medical facility is recommended.
- Sharing nail clippers is a route of infection for nail fungus (athlete's foot). One pair per person, even within a family, or disinfect after use.
[Verify] Check the square-off recommendation against materials from the Japanese Dermatological Association and the Japanese Society for Foot Care and Podiatric Medicine.
Misunderstanding 1｜Cut toenails short and round
The main cause of ingrown and pincer nails. Level with the toe tip, straight across, corners only.
Misunderstanding 2｜If the corner digs in, cut the corner deeper
A vicious circle: it digs in further. Let it grow and return to square-off. For pain or pus, see a dermatology or plastic-surgery clinic.
Misunderstanding 3｜Nail clippers can be shared within the family
A route of infection for nail fungus (athlete's foot). One per person, or disinfect.
Misunderstanding 4｜Thick cloudy nails are just age
It may be nail fungus. A dermatology clinic can test it (a few minutes); the medicine takes months. Left alone, it spreads to the feet as athlete's foot.
Misunderstanding 5｜Pincer nails have nothing to do with shoes
Pointed shoes, shoes that are too small and heels are among the main causes of pincer and ingrown nails. Leave room at the toes and fit the heel snugly (see our shoe article).
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Sources
- Japanese Dermatological Association, *Dermatology Q&A: Nail conditions (ingrown and pincer nails)* [皮膚科Q&A 爪の病気（陥入爪・巻き爪）]
https://www.dermatol.or.jp/qa/
- Japanese Society for Foot Care and Podiatric Medicine, *How to cut nails correctly* [正しい爪の切り方]
https://jfcpm.org/
- Japanese Dermatological Association, *Clinical Practice Guidelines for Dermatomycosis* [皮膚真菌症診療ガイドライン] (nail fungus)
https://www.dermatol.or.jp/uploads/uploads/files/guideline/
⚠️ 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.
This article is not meant to diagnose or manage any specific medical condition. If you are worried about your health, see a doctor rather than relying on your own judgement.
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