Specimen No. 0199
AvoidSyntheticcosmetic preservative
Methylchloroisothiazolinone
CAS 26172-55-4 · MCI · CMIT · Methylchloroisothiazolinone
A synthetic preservative, normally blended with methylisothiazolinone, that is a potent skin sensitizer implicated in the same contact-dermatitis epidemic.
high confidence
Researched July 7, 2026Specimen 0199Methylchloroisothiazolinone
Concerns
- The methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) blend is a widely used preservative for which a considerable increase in cases of contact dermatitis has been recorded, prompting calls for stricter legislation (Leiva-Salinas 2014, PMID 24626102)
- Tested at the older 100 ppm concentration, up to 50 percent of contact-allergy cases can go undetected, indicating a potent sensitizer that is easy to under-diagnose (Leiva-Salinas 2014, PMID 24626102)
- MCI/MI allergy formed part of the 2010 to 2015 global epidemic that peaked in 2013 and 2014 (Ozkaya 2020, PMID 32691417)
Regulatory flags
- ⚑IARC Class: NL
- ⚑EDC Status: Not established
- ⚑Regulatory: EU: restricted preservative (Annex V); US: permitted
- ⚑Evidence Grade: A
Commonly found in
Rinse-off cosmeticsShampooWet wipesHousehold cleanersWater-based paint
Sources & references
Last researched: July 7, 2026
Research disclaimer: This rating is based on available peer-reviewed research and regulatory assessments at the time of publication. It is not medical advice. Consult a qualified professional for personal health or skin concerns.
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