What do people get wrong about SPF and PA in Japan?
This answer is a draft. It stays unpublished until legal review and source verification are complete.
PA is the rating most visitors have never seen before. For the rest of the label, see #79.
Two scales, one test condition
| Rating | What it measures | Scale |
|---|---|---|
| SPF | Protection against UVB (the burning wavelengths) | A number, labelled up to SPF50+ in Japan |
| PA | Protection against UVA (longer wavelengths, penetrate deeper, pass through window glass) | PA+ to PA++++ |
Both are measured under international test methods with 2 mg of product per cm² of skin. Surveys report actual use at around a quarter to half of that. Applied thinly, neither rating behaves as printed.
[Verify] Test standard and actual-use figures from dermatology and industry sources. Confirm with Japan Cosmetic Industry Association material before publication.
Misunderstanding 1｜PA is a second opinion on SPF
SPF relates to UVB. PA relates to UVA. They are not two measures of the same thing.
Misunderstanding 2｜More plus signs is always the right choice
Choose for the situation. The highest is not automatically right for a short errand.
Misunderstanding 3｜A high SPF covers UVA too
A high SPF number says nothing on its own about UVA. Look for the PA rating separately. Since UVA passes through glass, PA is the rating that matters indoors by a window.
Misunderstanding 4｜The ratings mean the same everywhere
SPF testing is largely harmonised internationally (ISO 24444), but UVA labelling is not: Japan uses PA, the EU a UVA-in-a-circle mark, the US 'Broad Spectrum'. Do not convert a Japanese PA rating into a familiar foreign one in your head.
Misunderstanding 5｜The rating alone determines the result
See the test condition above. Amount decides whether the rating is real.
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Sources
- Japan Cosmetic Industry Association — UV protection measurement standards
https://www.jcia.org/
- Ministry of the Environment — Ultraviolet Radiation Health Manual
https://www.env.go.jp/chemi/uv/uv_manual.html
- Japanese Dermatological Association
https://www.dermatol.or.jp/qa/
⚠️ 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 intended to treat or prevent any condition. If you notice any irritation, stop using the product and consult a dermatologist. Always follow the instructions on the product.
Sources
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