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

Towle, Kevin M., SM*; Drechsel, Derek A., PhD; Warshaw, Erin M., MD, MS‡§; Fung, Ernest S., PhD; Novick, Rachel M., PhD*; Paustenbach, Dennis J., PhD; Monnot, Andrew D., PhD*

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.

From the *Cardno ChemRisk, San Francisco, CA;

Cardno ChemRisk, Boulder, CO;

Dermatology Department, University of Minnesota;

§Park Nicollet, Minneapolis, MN,

Cardno ChemRisk, Aliso Viejo, CA; and

Cardno ChemRisk, Jackson, WY.

Address reprint requests to Kevin M. Towle, SM, 101 2nd St, Suite 700, San Francisco, CA 94105. E-mail:

K.M.T., D.A.D., E.S.F., R.M.N., D.J.P., and A.D.M. are employed by Cardno ChemRisk, a consulting firm that provides scientific advice to the government, corporations, law firms, and various scientific/professional organizations. Cardno ChemRisk and E.M.W. have been engaged by WEN by Chaz Dean, which produces personal care products that may contain Kathon CG.

The study was supported by WEN by Chaz Dean.

This article was prepared and written exclusively by the authors without review or comment by any outside entity. It is possible that this work will be relied upon in litigation.

© 2018 American Contact Dermatitis Society
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