preservative

Methylchloroisothiazolinone

Restricted·Strong evidence

Methylchloroisothiazolinone is typically used together with methylisothiazolinone in a 3:1 mix and is a well-documented skin sensitizer at higher rates than most preservatives. EU rules now restrict this combination to rinse-off products only, at a low maximum concentration.

Worth knowing

Known contact sensitizer for some
Can irritate, especially left on
Restricted in the EU

EU permits the MCI/MIT (3:1) mixture only in rinse-off products at a maximum of 0.0015% (15 ppm); banned from leave-on products since 2017.

Gentler alternatives

Phenoxyethanol
Sodium Benzoate

Products with Methylchloroisothiazolinone

84
Aussie
3 Minute Miracle Moist Deep Conditioner
77
Olay
Olay Ultra Moisture Body Wash with Shea Butter
72
Old Spice
Swagger Body Wash

References

EU CosIng entry: Methylchloroisothiazolinone ↗
CIR ingredient search: Methylchloroisothiazolinone ↗

Cosmetic information for general education, not medical advice. A verdict is a reading of the published evidence, never a guarantee for your skin: any ingredient can irritate someone, so patch test new products and see a professional if you react. Concern is graded on cited evidence, never on hazard-score lists. See how we score.