Risk Assessment of the Skin Sensitization Induction Potential of Kathon CG in Rinse-off and Leave-on Personal Care and Cosmetic Products

Dermatitis. 2018 May/Jun;29(3):132-138. doi: 10.1097/DER.0000000000000359.


Background: Kathon CG is a commonly used cosmetic-grade preservative that contains active ingredients methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI).

Objective: The aim of the study was to perform a skin sensitization induction risk assessment of daily exposure to Kathon CG after use of various personal care and cosmetic products.

Methods: We calculated an estimated daily consumer exposure level for rinse-off and leave-on products using the amount of product applied per application, number of applications per day, a retention factor, the MCI/MI concentration, and body surface area values. We assumed that the products contained the maximum recommended safe concentration of MCI/MI: 15 ppm in rinse-off products and 7.5 ppm in leave-on products. We compared estimated consumer exposure levels with the no expected sensitization induction level for MCI/MI and applied sensitization assessment factors to calculate product-specific margins of safety (MOSs).

Conclusions: The MOSs for rinse-off products ranged from 5 to 63, whereas the MOSs for leave-on products ranged from 0.03 to 1.49. Overall, our results provide evidence that some leave-on products containing the maximum recommended safe concentration of Kathon CG may increase the risk of sensitization induction due to exposure to MCI/MI. In contrast, rinse-off products were not associated with a potential increased risk of skin sensitization induction.

MeSH terms

  • Cosmetics / adverse effects
  • Cosmetics / analysis
  • Cosmetics / pharmacology
  • Dermatitis, Allergic Contact / diagnosis*
  • Dermatitis, Allergic Contact / etiology
  • Female
  • Humans
  • Preservatives, Pharmaceutical / adverse effects*
  • Preservatives, Pharmaceutical / analysis
  • Preservatives, Pharmaceutical / pharmacology
  • Risk Assessment
  • Skin / drug effects
  • Thiazoles / adverse effects*
  • Thiazoles / analysis
  • Thiazoles / pharmacology


  • Cosmetics
  • Preservatives, Pharmaceutical
  • Thiazoles
  • 2-methyl-4-isothiazolin-3-one
  • Kathon 886
  • 5-chloro-2-methyl-4-isothiazolin-3-one