Methylchloroisothiazolinone
Strong preservative from the isothiazolinone family (CMIT). The EU banned it in leave-on cosmetics from 2015 due to a contact allergy epidemic.
Evidence by route
Topical application
One of the strongest contact sensitizers in cosmetics on record. Rinse-off products tolerate it only at low concentrations up to 15 ppm.
How to read tiers A–F
- DNo data, or very weak or conflicting data
Tolerability and safety
- Irritation potential
- High
- Allergen risk
- High
- Pregnancy
- Caution
- Use with caution
- Sensitive, Dry
About this ingredient
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.
Frequently asked questions
Is Methylchloroisothiazolinone safe during pregnancy?
Methylchloroisothiazolinone should be used with caution during pregnancy. Consulting a dermatologist or OB-GYN is advisable.
What skin types is Methylchloroisothiazolinone for?
Use with caution in: sensitive, dry.
Can Methylchloroisothiazolinone irritate the skin?
Yes, Methylchloroisothiazolinone has high irritation potential. Start at low concentrations, introduce gradually, and always use SPF during the day.
Can Methylchloroisothiazolinone cause an allergic reaction?
Methylchloroisothiazolinone has high allergen potential. Perform a patch test on the inner forearm 24 hours before facial application.
What is Methylchloroisothiazolinone and what does it do in cosmetics?
Strong preservative from the isothiazolinone family (CMIT).
What's the INCI name for Methylchloroisothiazolinone?
The INCI name is Methylchloroisothiazolinone. It may also appear as: CMIT, CMI, Methylchloro Isothiazolinone.
See Methylchloroisothiazolinone in a product composition right on the store page
The Evigrade extension adds an evidence panel to iHerb, Sephora, Druni and 12 more stores. This ingredient and every other one in the product show evidence-tier, allergen risk and pregnancy/lactation flags at a glance.
Similar in action
More ingredients in the database
Methylisothiazolinone, Minoxidil, Mixed Fruit Extract, Myrtus Communis Oil, Rosa Damascena Flower Extract, Benzyl Benzoate, Copaifera Officinalis Resin, Grapefruit Peel Oil
Published: · updated: