Methylisothiazolinone — Allergy Risk & Safety Profile
INCI: METHYLISOTHIAZOLINONE
Also known as: MI, MIT, Neolone 950
Key Facts
- CAS Number
- 2682-20-4
- Category
- preservative
- Risk Level
- high
- Common Allergen
- Yes
- EU Status
- Restricted
- Max Concentration
- 0.0015% (rinse-off only, leave-on banned)
- Found In
- shampoo, conditioner, body wash, cleaning products
Is Methylisothiazolinone safe in cosmetics?
Methylisothiazolinone is rated high risk in cosmetic products. It is a known allergen that can cause contact dermatitis in sensitized individuals. Preservative linked to high rates of allergic contact dermatitis. The most common cosmetic allergen identified in patch testing. This ingredient is restricted under EU cosmetic regulations. Safer alternatives include Phenoxyethanol, Sodium Benzoate, Potassium Sorbate. Commonly found in shampoo, conditioner, body wash.
What is Methylisothiazolinone?
One of the most common contact allergens in cosmetics. Banned in leave-on products in the EU since 2016.
Allergy & Safety Information
Methylisothiazolinone is classified as a high-risk ingredient. It is a known cause of allergic contact dermatitis. It is restricted or regulated in the EU. Individuals with sensitive skin or a history of contact allergies should avoid products containing this ingredient. A patch test is recommended before first use of any product containing Methylisothiazolinone.
This ingredient is classified as high risk from an allergenicity perspective. It is a recognised cause of allergic contact dermatitis with a relatively high sensitisation rate in patch-tested populations. People with a history of skin reactions to cosmetics, or with conditions such as eczema or sensitive skin, should exercise particular caution.
About Preservative Ingredients
Preservatives prevent microbial growth in water-containing cosmetic formulas. Without them, products would spoil within days. However, preservatives are among the most common causes of allergic contact dermatitis — they must be present in high enough concentrations to be effective, yet that same efficacy can irritate sensitised skin.
Relevance for Methylisothiazolinone: If you react to one preservative, you may be cross-reactive to others in the same chemical family (e.g., isothiazolinones, formaldehyde releasers, or parabens). Checking the full preservative profile of every product you use is the most reliable way to identify your personal trigger.
How to Identify Methylisothiazolinone in Products
Cosmetic ingredients are listed by their INCI (International Nomenclature of Cosmetic Ingredients) name in descending order of concentration. To check whether a product contains Methylisothiazolinone, scan the ingredient list for its INCI name exactly as it appears above. Ingredients present at 1% or less may appear in any order after the 1% threshold.
Product types to prioritise checking: Shampoo, Conditioner, Body wash, Cleaning products. These product categories are the most common sources of Methylisothiazolinone exposure based on formulation data.
Not sure if your products contain Methylisothiazolinone? Paste the ingredient list into the free ingredient checker to scan for Methylisothiazolinone and other allergens automatically.
Cross-Reactions
If you react to Methylisothiazolinone, you may also react to:
Safer Alternatives
These ingredients serve a similar function with lower allergy risk:
Frequently Asked Questions
Is Methylisothiazolinone safe for sensitive skin?
Methylisothiazolinone is a known allergen and is generally not recommended for sensitive skin. Consider patch testing before use.
What products contain Methylisothiazolinone?
Methylisothiazolinone is commonly found in shampoo, conditioner, body wash, cleaning products.
What does Methylisothiazolinone do in cosmetics?
Methylisothiazolinone functions as a preservative in formulations. Preservative linked to high rates of allergic contact dermatitis. The most common cosmetic allergen identified in patch testing.
Related Guides
Top 10 Cosmetic Allergens
Is Methylisothiazolinone on the list? See the full clinical ranking.
Preservative Allergy Guide
Which preservatives cause the most reactions and what to use instead.
How to Read Ingredient Labels
Decode INCI names and find hidden allergens in your products.
Find Your Skin Allergy Trigger
Step-by-step elimination method to identify your trigger.
Contact Dermatitis Guide
Symptoms, causes, patch testing, and treatment options.
Is Methylisothiazolinone causing YOUR skin reactions?
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