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Preservative

METHYLCHLOROISOTHIAZOLINONE

CAS 26172-55-4
22

Safety score · 0–100

Caution

Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.

A potent isothiazolinone preservative — extremely effective but one of the worst contact sensitizers on the market. EU-banned in leave-on, severely restricted in rinse-off only.

Skin benefits

  • Highly effective broad-spectrum preservative at low ppm

Known concerns

  • Severe contact sensitizer — one of the most common allergens
  • EU bans in leave-on products since 2015
  • Restricted to ≤0.0015% in rinse-off only (as MCI/MI 3:1)
  • Allergy may persist for life once developed

References

EU

EU CosIng database

European Commission cosmetic ingredient registry: regulatory status, restrictions, authorised functions.

PC

PubChem

U.S. NIH compound data, GHS hazard codes and toxicity literature.

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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.