Back to Ingredient Dictionary

Methylchloroisothiazolinone

Description

Methylchloroisothiazolinone (MCI) is a potent synthetic biocide and preservative commonly used in personal care products, cosmetics, and industrial applications. This water-soluble compound belongs to the isothiazolinone family and is often used in conjunction with methylisothiazolinone (MI) for enhanced antimicrobial efficacy. MCI effectively inhibits the growth of bacteria, yeasts, and fungi, extending the shelf life of various formulations.

The ingredient's primary function is to prevent microbial contamination, ensuring product safety and stability. MCI is particularly effective at low concentrations, typically ranging from 0.0015% to 0.01% in leave-on and rinse-off products. However, its use is regulated due to potential skin sensitization concerns.

While MCI offers excellent preservation properties, it has been associated with allergic contact dermatitis in some individuals. As a result, many manufacturers have begun to explore alternative preservatives or use it at reduced concentrations. In the European Union, MCI is restricted in leave-on products and must be declared on product labels when used in rinse-off formulations at certain concentrations. Formulators must carefully balance the preservative efficacy of MCI with potential skin sensitization risks when incorporating it into skincare and cosmetic products.