Methylisothiazolinone

METH-ul-eye-so-thy-AZ-oh-lin-own

Preservative 2/10 Safety Not CGAvoid Synthetic Vegan

What Is Methylisothiazolinone?

A synthetic preservative used to prevent microbial growth in hair and personal care products. It has come under significant scrutiny for causing contact allergies and skin sensitization.

Source: Synthetic organic compound

Origin: Synthetic

Also known as: MIT, MI, Neolone 950

What Does Methylisothiazolinone Do to Your Hair?

Provides potent antimicrobial preservation even at very low concentrations. Effective against bacteria, yeast, and mold. However, its strong sensitization potential has led to widespread reformulation away from this ingredient.

Best For

None recommended

Not Recommended For

All hair types, especially sensitive scalp, eczema-prone skin, children

Concentration Matters

Up to 100 ppm (0.01%) in rinse-off products; banned in leave-on in EU

Hair Type Compatibility

1A Straight Fine
1B Straight Medium
1C Straight Coarse
2A Wavy Fine
2B Wavy Medium
2C Wavy Coarse
3A Curly Loose
3B Curly Tight
3C Curly Corkscrew
4A Coily S-Shaped
4B Coily Z-Shaped
4C Coily Tight

Method Compatibility

Curly Girl (CG) Method: Avoid
CG Avoid

Safety & Regulation

2/10
AvoidCautionSafe

Significant allergen and sensitizer. The EU banned MIT in leave-on cosmetics in 2016 and restricted it in rinse-off products. A leading cause of contact dermatitis worldwide. Avoid if at all possible.

FDA Status: Restricted

FDA permits use but the EU has banned it in leave-on products and restricted concentration in rinse-off products to 15 ppm.

EWG Score: 7/10

HairAide Verdict

Avoid this ingredient. It is a potent sensitizer that has caused widespread contact dermatitis. Many brands have already reformulated to remove it. Choose products preserved with safer alternatives.

Products That Contain Methylisothiazolinone

Some shampoos, rinse-off conditioners (being phased out)

Alternatives to Methylisothiazolinone

If you want to avoid Methylisothiazolinone, look for products with these ingredients instead:

Phenoxyethanol, Benzyl Alcohol, Sodium Benzoate, Sorbic Acid

Frequently Asked Questions

Is Methylisothiazolinone safe for hair?

Methylisothiazolinone has a safety rating of 2/10 and may be problematic for many hair types. Significant allergen and sensitizer. The EU banned MIT in leave-on cosmetics in 2016 and restricted it in rinse-off products. A leading cause of contact dermatitis worldwide. Avoid if at all possible.

Is Methylisothiazolinone bad for curly hair?

Methylisothiazolinone is not CG-method approved. Curly hair types may want to avoid this ingredient or use products containing it sparingly.

Is Methylisothiazolinone CG-method approved?

No, Methylisothiazolinone is not approved for the Curly Girl method.

What can I use instead of Methylisothiazolinone?

Some alternatives to Methylisothiazolinone include: Phenoxyethanol, Benzyl Alcohol, Sodium Benzoate, Sorbic Acid

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