What does Methylisothiazolinone do for skin?

Methylisothiazolinone is a preservative used in K-beauty for Preservative, Antimicrobial. The preservative the American Contact Dermatitis Society named "Allergen of the Year" in 2013 — for a reason.

Is Methylisothiazolinone safe during pregnancy?

There is limited safety data on Methylisothiazolinone during pregnancy. Exercise caution and consult your healthcare provider before use.

How strong is the evidence for Methylisothiazolinone?

We rate the clinical evidence for Methylisothiazolinone at 2/5 — limited. Legal max in EU leave-on: 0.0015%. Rinse-off: 0.0015%.

preservativeOverhyped

Methylisothiazolinone

Also known as: MIT, MI

2/5— Limited Evidence

Medically reviewed by ChokChok · Updated April 15, 2026

The preservative the American Contact Dermatitis Society named "Allergen of the Year" in 2013 — for a reason.

What It Does

PreservativeAntimicrobial

Deep Dive

Methylisothiazolinone (MIT or MI) is a preservative that was widely adopted in the 2000s as a replacement for parabens. It turned out to be an unusually potent contact sensitizer — rates of contact dermatitis caused by MIT tripled between 2010 and 2015. The EU has tightened restrictions significantly; the US is more permissive. If you have reactive skin, check your INCIs for this one and avoid leave-on products containing it.