Methylisothiazolinone

MI is a preservative and known skin irritant. In the past, MI was used for its ability to prevent bacteria, yeast, and fungi growth in low doses.

Nowadays, you'll most likely see MI combined with Methylchloroisothiazolinone (MCI). Trade names for this combination include Kathon CG or Euxyl K 100.

Since then, numerous studies have shown this ingredient to cause contact dermatitis, or skin irritation.

The use of this ingredient varies around the world:

• The EU has banned this ingredient for leave-on products and it is capped at 0.0015% for rinse-off products.
• The US allows this ingredient in concentrations of up to 15 parts per million (ppm) in rinse-off products and 8 ppm in other products.
• Canada allows this ingredient to be used with MCI in rinse-off products. The combination must not exceed 0.0015%.