The Cosmetic Ingredient Review’s Expert Panel determined the preservative mixture of methylchloroisothiazolinone and methylisothiazolinone (MCI/MI) safe for use at its 9-10 December meeting in Washington, albeit with stipulations concerning sensitization potential.
The MCI/MI combo (in a roughly 3:1 ratio) can be used safely in rinse-off and leave-on cosmetics at maximum concentrations of 15 parts per million and 7.5 ppm, respectively, when formulated to be non-sensitizing, according to the final panel decision summarized in CIR’s