Methylisothiazolinone (MI) and Methylchloroisothiazolinone (MCI) are preservatives.  Preservatives are natural or man-made ingredients designed to help ensure the safety and quality of products by protecting them against the growth of microorganisms during storage and, most importantly, during use by consumers.  Any product that contains water is particularly susceptible to being spoiled by microbial growth, causing problems such as discoloration, unpleasant odors or breakdown. Under certain conditions, microorganisms can even grow to potentially harmful levels. Preservatives are designed to help prevent these problems.

Although Methylisothiazolinone (MI) may be used in cosmetics and personal care products alone, it is often used as a mixture with Methylchloroisothiazolinone [(MCI). In cosmetics and personal care products historically, Methylisothiazolinone, or the mixture, Methylisothiazolinone and Methylchloroisothiazolinone, was used in various rinse-off and leave-on formulations including hair products, shampoos, skin care products, bath products, eye and facial makeup, wet wipes and suntan products.  More recently, due to concerns being raised about potentially increasing rates of skin sensitivity to MI, some cosmetic and personal care product manufacturers have begun removing it from leave-on products such as lotions and wipes (see more under ‘SAFETY’ tab).

Follow this link for more information about how preservatives protect cosmetics and personal care products.

Cosmetic products can become contaminated through consumer use.   The product itself may come into contact with the skin potentially exposing the product to bacteria and fungi naturally found on our skin. Consumers may also use and store cosmetic products, like shower gels, in warm and moist conditions, ideal for microbial growth.  As such, the inclusion of ingredients which are capable of preventing or inhibit microbial growth is critical to assuring the quality and safety of cosmetic products.