Value Village / Beauty

What are the common misunderstandings about emulsions and serums?

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 It stays unpublished until legal review and source verification are complete.

The answerThe biggest misunderstanding is "an emulsion and a serum both 'put active ingredients in', so one or the other will do." In Japanese usage they have different jobs. An emulsion mixes water and oil and acts as a "lid" that slows the evaporation of water from the skin. A serum "adds" a higher level of a particular ingredient. Legally, however, both are "cosmetics", and the claims they may make are the same 56 items.

Japanese skincare has many steps: lotion (化粧水, keshōsui — a watery toner), serum (美容液, biyōeki), emulsion (乳液, nyūeki — a light, milky moisturiser) and cream. Visitors often ask why there are so many stages, and what an "emulsion" actually is. Here we sort the products by their legal category and their role.

Roles (the customary classification)

ProductMain roleTextureLegal category
Lotion (化粧水, keshōsui)Gives water; helps the next product spreadWateryCosmetic
Serum (美容液, biyōeki)Adds a higher level of particular ingredients (moisturising or skin-conditioning ingredients, etc.)Gel to slightly thickCosmetic (some are quasi-drugs)
Emulsion (乳液, nyūeki)Adds water and oil, and slows evaporationMilky (oil-in-water)Cosmetic
CreamMore oil; a firmer lidThickCosmetic
[Verify] Check the 56 items against MHLW notice Yakushoku-hatsu 0721 No. 1, and the scope of quasi-drug claims against Ministry of Health, Labour and Welfare (MHLW) materials. "Makes fine lines caused by dryness less visible" is wording based on the Japan Cosmetic Industry Association's efficacy evaluation test guideline.

Misunderstanding 1|An emulsion is oil, so oily skin does not need one

The oil content of emulsions varies widely between products, and light, fresh types exist. The basic idea in Japanese skincare is that if you add water and put no lid on it, the water evaporates and the skin dries (see our article on oily skin).

Misunderstanding 2|The more expensive the serum, the better it works

Cosmetic serums all share the same range of permitted claims; the differences are in ingredients and formulation. The quasi-drug label and its active ingredient tell you more than the price does.

Misunderstanding 3|The more serums you layer, the better

Layering several serums can stack up irritating ingredients, or leave product sitting unabsorbed on the skin. The usual advice is to pick one or two goals.

Misunderstanding 4|Lotion after emulsion penetrates better

The customary order is from the most watery product to the most oily. Lotion after emulsion means putting water on top of a film of oil. Products the maker has designed as a "pre-emulsion" (先行乳液, senkō nyūeki) are the exception — follow the label.

Misunderstanding 5|A Western "moisturiser" is the same as an emulsion

A "moisturiser" abroad is closer to emulsion and cream combined; it is not split as finely as in Japan. Replacing "lotion → serum → emulsion" with a single moisturiser can work perfectly well, depending on your skin type.

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Sources

https://www.mhlw.go.jp/file/06-Seisakujouhou-11120000-Iyakushokuhinkyoku/kesyouhin_hanni_20111.pdf

https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/iyakuhin/keshouhin/index.html

https://www.jcia.org/user/business/

⚠️ 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.

Sources

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