Methylisothiazoinone ●
TL;DR. This ingredient is a synthetic preservative used to control bacteria, yeast, and mold in water-based personal care formulas. It is most associated with rinse-off products and other high-water systems that need broad microbial protection at very low levels.
What does Methylisothiazoinone do in a cosmetic formula?
This ingredient is a synthetic preservative used to control bacteria, yeast, and mold in water-based personal care formulas. It is most associated with rinse-off products and other high-water systems that need broad microbial protection at very low levels.
Is Methylisothiazoinone clean?
This ingredient has significant clean-standard friction because it is a well-known contact sensitizer and is heavily restricted in several regulatory markets. In the EU, it is not allowed in leave-on cosmetics and is capped at very low levels in rinse-off products.
Is Methylisothiazoinone sustainable?
This material is synthetically produced, typically from petrochemical-derived feedstocks, rather than sourced from renewable agricultural inputs. It is used at tiny concentrations, but its aquatic-life profile and non-renewable sourcing make it a weak sustainability fit.
Is Methylisothiazoinone COSMOS-approved?
This ingredient is not permitted under COSMOS-natural or COSMOS-organic standards. From a Green Chemistry perspective, it has limited alignment because it is synthetic, non-renewable in typical production, and carries sensitization and aquatic-life concerns despite very low use levels.
How does Methylisothiazoinone work chemically?
The molecule is a small heterocyclic preservative built around an isothiazolinone ring, which reacts with microbial enzymes and proteins to disrupt cell function. Typical cosmetic limits are very low, with EU rinse-off use capped at 0.0015 percent, and formulators usually pair it with other preservation controls rather than relying on higher dosing.
Last updated 2026-08-31