INGREDIENTS WE AVOID #4 - Methylisothiazolinone

INGREDIENTS WE AVOID #4 - Methylisothiazolinone

We have researched and decided not to use the preservative Methylisothiazolinone (MI). It is a long and very hard to remember name – but the evidence is building that it is simply not safe. The NY Times recently reported on the increasing irritation people are experiencing from it. Depending on the product, reported reactions range from mild irritation, through to scarring of the skin.


Methylisothiazolinone is a preservative used increasingly since 2010 in many brand name and ‘natural’ brands looking for paraben free preservative systems. You’ll usually find it towards the end of ingredient listings as concentrations are small – but even so it has caused alarming reactions.

The dermatitis society named it ‘allergen of the year’ in 2013. Europeans outlawed it in leave-on products a year ago and have restricted its concentration in rinse-off products. In the US, Unilever and Johnson & Johnson have begun phasing it out in leave-on products and are looking for alternatives in rinse-off products.

In Korea in 2016, Reckitt-Coleman used it in a humidifier cleaner which resulted in the death of over 100 people and extensive lung damage in many others.  Koreans are very wary of this preservative now and it is highly regulated.

Some companies are now using the tag ‘MI free’ but the only way to check is to read the ingredients listings or email the company if they don’t list their preservatives. Look for it in baby wipes, mouthwashes, hand creams, makeup and cleaning products. It is definitely one we now avoid.