Methylisothiazolinone: what it is in skincare
A potent preservative used in very small amounts, mainly in rinse-off products; a frequent contact allergen now restricted in leave-on products.
What it does
Function: preservative. Preservatives keep water-based formulas safe from microbial growth. Modern, well-tolerated systems are why your essence stays safe for months.
- sensitive-skin-caution
- allergen
How to spot it on a label
On a Korean product's INCI list, look for Methylisothiazolinone. Ingredients are listed high-to-low by amount, so its position hints at how much is in the formula. See all preservatives →
Explore the full K-beauty hub →✍️ Written & reviewed by the KoreaPlus Editorial team — dermatologist-informed, cosmetic-science researched & source-cited. Last reviewed 2026-06-21.
General educational information using cosmetic structure-function wording — not medical advice. Always patch-test new actives. © KoreaPlus.