Methylisothiazolinone ●
TL;DR. This ingredient is a high-efficacy preservative used to control bacteria, yeast, and mold in water-based beauty and personal care formulas. It is most associated with rinse-off products, where very low use levels can protect a formula from microbial growth.
What does Methylisothiazolinone do in a cosmetic formula?
This ingredient is a high-efficacy preservative used to control bacteria, yeast, and mold in water-based beauty and personal care formulas. It is most associated with rinse-off products, where very low use levels can protect a formula from microbial growth.
Is Methylisothiazolinone clean?
From a clean beauty perspective, this ingredient has major friction because it is a well-documented skin sensitizer and is heavily restricted in several markets. It is generally not accepted by stricter clean standards, especially for leave-on products and products marketed for sensitive skin.
Is Methylisothiazolinone sustainable?
This material is synthetically produced, typically from petrochemical feedstocks. It is used at very low concentrations and is not known as a major persistence concern, but its aquatic organism profile and synthetic origin limit its sustainability standing.
Is Methylisothiazolinone COSMOS-approved?
This ingredient is not permitted under COSMOS-natural or COSMOS-organic standards. Its profile does not align strongly with Green Chemistry priorities because it is synthetic, highly biologically active at trace levels, and restricted by major regulatory frameworks.
How does Methylisothiazolinone work chemically?
The molecule is a small sulfur- and nitrogen-containing heterocycle that preserves formulas by reacting with microbial enzyme systems. In the EU, it is not allowed in leave-on cosmetics and is limited to 0.0015 percent in rinse-off products, with performance generally best in water-based systems across mildly acidic to neutral pH ranges.
Last updated 2026-05-13