Strong preservative from the isothiazolinone family (CMIT). The EU banned it in leave-on cosmetics from 2015 due to a contact allergy epidemic.
Topical application
DVery weak or conflicting data.
One of the strongest contact sensitizers in cosmetics on record. Rinse-off products tolerate it only at low concentrations up to 15 ppm.
Methylchloroisothiazolinone (MCI) is a synthetic preservative from the isothiazolinone family. Used in a 3:1 blend with methylisothiazolinone (MI) (Kathon CG). Mechanism. Inhibits respiratory chain enzymes in microorganisms by forming covalent bonds with thiol groups. Effective against bacteria, fungi, mold. Where applied. Rinse-off products only (shampoos, shower gels, conditioners) since 2015. Banned in leave-on products in the EU since 2015 due to high contact allergy rates. Maximum concentration under EU Regulation 1223/2009 – 0.0015% (15 ppm) of the 3:1 MCI/MI mixture. Evidence base. Epidemiology. According to the European Surveillance System on Contact Allergies (ESSCA), MCI/MI is among Europe's top 10 contact allergens. Sensitization rate in the general population – 1.5–4% (Uter 2017). The EU requires separate labeling since 2017. Safety. SCCS confirmed safety in rinse-off products only at up to 15 ppm. Leave-on – banned. Sensitized patients develop eczema and contact dermatitis from even minimal contact. Pregnancy and lactation – use with caution. Systemic absorption in rinse-off products at approved concentrations is minimal, the risk is low. Strict avoidance in patients with known sensitization. Alternative preservatives – phenoxyethanol, sodium benzoate, pentylene glycol.
Irritation potential
HighAllergen risk
HighPregnancy
CautionUse with caution
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Methylchloroisothiazolinone should be used with caution during pregnancy. Consulting a dermatologist or OB-GYN is advisable.
Use with caution in: sensitive, dry.
Yes, Methylchloroisothiazolinone has high irritation potential. Start at low concentrations, introduce gradually, and always use SPF during the day.
Methylchloroisothiazolinone has high allergen potential. Perform a patch test on the inner forearm 24 hours before facial application.
Strong preservative from the isothiazolinone family (CMIT).
Published: · updated:
The INCI name is Methylchloroisothiazolinone. It may also appear as: CMIT, CMI, Methylchloro Isothiazolinone.