GoodSwap Get notified

Beauty ingredient · Preservative

Methylchloroisothiazolinone (MCI)

CAS
26172-55-4

A preservative used only in a 3:1 mixture with MIT; a strong contact allergen.

  • Isothiazolinone preservative
  • Preservative
  • Expert review pending
High concern Level 3 of 4 How concern levels work

A regulatory warning or restriction somewhere, or strong evidence of harm at typical intake. The concern level sets how many points methylchloroisothiazolinone (MCI) costs on a product’s receipt.

What the evidence says

  • Contact allergenRegulatory

    A frequent cause of contact allergy; the EU banned methylisothiazolinone in leave-on products (2017) and limits it to 0.0015% in rinse-off products. [1][2][3]

Evidence tiers say how sure the evidence is, separately from how much it matters. About evidence tiers.

Rules around the world

WhereStatusDetailsDateSource
European Union Restricted MCI/MIT (3:1) only in rinse-off products, up to 0.0015%. — [3]
Canada Restricted MI/MCI in combination: not permitted in leave-on products; rinse-off up to 0.0015%. — [4]

“Banned” means explicitly prohibited or withdrawn after review; “not permitted” means never authorized there. We use each regulator’s own words.

Names GoodSwap recognizes on labels (10)
  • mci
  • mci mit
  • kathon cg
  • methylchloroisothiazolinone
  • methylchloroisothiazolinone mci
  • methylchloroisothiazolinone mixture
  • 5 chloro 2 methyl 4 isothiazolin 3 one
  • methylchloroisothiazolinone methylisothiazolinone
  • methylchloroisothiazolinone and methylisothiazolinone
  • methylchloroisothiazolinone and methylisothiazolinone mixture

Sources

  1. Commission Regulation (EU) 2016/1198 of 22 July 2016 amending Annex V to Regulation (EC) No 1223/2009 (Methylisothiazolinone in leave-on products)

    European Union (Official Journal) · Jul 22, 2016 · Law

    “this substance should therefore be banned in leave-on products.”

    eur-lex.europa.eu

  2. Commission Regulation (EU) 2017/1224 of 6 July 2017 amending Annex V to Regulation (EC) No 1223/2009 (Methylisothiazolinone in rinse-off products)

    European Union (Official Journal) · Jul 6, 2017 · Law

    “a concentration up to 0,0015 % (15 ppm) Methylisothiazolinone is considered safe for the consumer from the point of view of induction of contact allergy.”

    eur-lex.europa.eu

  3. Commission Regulation (EU) No 1003/2014 of 18 September 2014 amending Annex V to Regulation (EC) No 1223/2009 (Methylchloroisothiazolinone and Methylisothiazolinone)

    European Union (Official Journal) · Sep 18, 2014 · Law

    “up to a maximum authorised concentration of 0,0015 % in rinse-off cosmetic products, apart from its skin sensitising potential.”

    eur-lex.europa.eu

  4. Cosmetic Ingredient Hotlist: prohibited and restricted ingredients

    Health Canada · Aug 13, 2025 · Regulator

    “The following ingredients are only permitted in cosmetic products under the conditions of use specified below:”

    canada.ca