Ask KBeauty Verified™

KBeauty Verified™ — K-beauty checked against official records from Korea, the EU and the U.S.

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Cysteine, acetylcysteine, and their salts

Korean: 시스테인, 아세틸시스테인 및 그 염류 ·

KR South Korea (MFDS)

Restricted MFDS restricted ingredients

Conditions (official MFDS text, Korean):
* 배합한도 : 퍼머넌트웨이브용 제품에 시스테인으로서 3.0~7.5% (다만, 가온2욕식 퍼머넌트웨이브용 제품의 경우에는 시스테인으로서 1.5～5.5%, 안정제로서 치오글라이콜릭애씨드 1.0%를 배합할 수 있으며, 첨가하는 치오글라이콜릭애씨드의 양을 최대한 1.0%로 했을 때 주성분인 시스테인의 양은 6.5%를 초과할 수 없다)

Source: MFDS — cosmetic ingredient use restrictions · checked Oct 16, 2026

EU European Union (CosIng)

No specific rule on file.

US United States (FDA)

No specific rule on file. The FDA regulates few cosmetic ingredients by name; no rule does not mean approval.

Also listed as

Cysteine, acetylcysteine, and their salts 시스테인, 아세틸시스테인 및 그 염류

Information only, not medical advice. Rules change — always check the linked official source. If you are pregnant, have a skin condition or allergies, ask a dermatologist or pharmacist.

Frequently asked questions

Is Cysteine, acetylcysteine, and their salts banned in the European Union?

We found no specific rule for it in the EU's CosIng records. That is not an approval or a safety statement.

Is Cysteine, acetylcysteine, and their salts banned in South Korea?

In Korea's MFDS records it is listed as “Restricted” (MFDS — cosmetic ingredient use restrictions). A restricted ingredient is allowed within the stated conditions.

Is Cysteine, acetylcysteine, and their salts allowed in cosmetics in the U.S.?

We found no specific rule for it in the FDA's records. That is not an approval or a safety statement.

What is Cysteine, acetylcysteine, and their salts called on Korean labels?

Korea's MFDS standard Korean name is 시스테인, 아세틸시스테인 및 그 염류.