What it is
Methylisothiazolinone is an organic compound (a substance that contains carbon and hydrogen and usually other elements such as nitrogen, sulfur and oxygen).
What it does
Methylisothiazolinone is a preservative that kills bacteria. However, it’s not very effective against fungi.
Methylisothiazolinone can be irritating. For this reason, it is mostly used in rinse-off products. The concentrations in leave-on products are restricted to a minimal amount to lessen the risk of a negative reaction.