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Methylisothiazolinone

What Methylisothiazolinone is & what it does

A potent preservative effective at very low levels, but a notable contact allergen that has been restricted to rinse-off uses in many regions. It protects formulas but is a common cause of sensitization.

What does Methylisothiazolinone do in skincare?

Methylisothiazolinone is a preservative used to protect water-containing products such as lotions and sunscreens from bacterial and fungal growth. By controlling microbial contamination, it helps keep a product stable and safe to use over its shelf life. It is a functional preservative rather than a skin active.

Is Methylisothiazolinone safe?

Methylisothiazolinone is an approved cosmetic preservative, but it is also a known contact allergen and is one of the more common causes of preservative sensitivity. Because of this, its use is restricted in many regions and it is typically limited to low concentrations or rinse-off products. People with known sensitivity to it generally prefer to avoid products that contain it.

Is Methylisothiazolinone natural or synthetic?

Methylisothiazolinone is a synthetic ingredient produced by chemical synthesis. It is not derived from a plant or animal source. It is manufactured specifically to serve as a preservative in water-based formulas.

Sunscreens with Methylisothiazolinone

We rate 87 sunscreens that contain it, showing the top 10 by overall score:

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