Preservative
METHYLISOTHIAZOLINONE
Safety score · 0–100
Caution
Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.
A preservative that triggered a major contact-allergy epidemic. EU banned it from leave-on cosmetics in 2017; rinse-off use is now capped at 0.0015%.
Function
Skin benefits
- Effective broad-spectrum preservative at low %
- Active against gram-negative bacteria
Known concerns
- Potent skin sensitizer
- EU banned in leave-on products since 2017
- Restricted to 0.0015% in rinse-off
- One of top contact allergens of the decade
References
EU CosIng database
European Commission cosmetic ingredient registry: regulatory status, restrictions, authorised functions.
PubChem
U.S. NIH compound data, GHS hazard codes and toxicity literature.
Frequently Asked Questions
Answers in plain language
Is methylisothiazolinone banned in Europe?
Partially. The EU banned methylisothiazolinone (MI) in leave-on cosmetic products in 2016 (Regulation 2016/1198) after a sharp rise in contact allergy cases. It is still permitted in rinse-off products at a maximum concentration of 0.0015% (15 ppm). Mixtures with methylchloroisothiazolinone (MI/MCI) are also restricted to rinse-off products only.
What are the side effects of methylisothiazolinone?
Contact allergy is the dominant concern. Between 2010 and 2014, MI caused an unusually rapid increase in sensitization across Europe, prompting the leave-on ban. Symptoms include eczema-like reactions where the product is applied. Already-sensitized individuals must avoid all isothiazolinone preservatives, including in non-cosmetic products like wall paint and cleaners.
Related preservatives
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This profile is for educational purposes and does not constitute medical advice. Regulatory status and scientific understanding evolve, so always read the physical product label and consult a healthcare professional for personal concerns.