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Avoid
preservative

Methylisothiazolinone

Methylisothiazolinone

Characteristics

INCI
Methylisothiazolinone
CAS
2682-20-4
EC
220-239-6
IUPAC
2-Methyl-2H-Isothiazol-3-One
Functions
preservative
EU Restr.
V/57 Rinse-off products 0,0015 % V/39 Mixture of 5-Chloro-2-methyl-isothiazol-3(2H)-one and 2-Methyl-2H-isothiazol-3-one

Who it's for

Face Concern
▼ Sensitive Skin ▼ Rosacea ▼ Eczema
Hair Concern
▼ Dandruff ▼ Flaky scalp ▼ Hair Loss ▼ Frizz ▼ Damage ▼ Split Ends ▼ Hydration ▼ Scalp Health ▼ Sensetive Scalp
Application Area
▲ Face ▲ Body ▲ Hair ▲ Scalp
methylisothiazolinone is the heterocyclic organic compound

Description

As you may guess, if something is only recommended in products that you rinse off (cleansers and shampoos), then it’s probably not the best ingredient for the skin.

Methylisothiazolinone (MI) is a preservative that' super efficient against bacteria at surprisingly low concentrations. The problem with it though is that it can also sensitize and irritate the skin quite easily when it comes in leave-on formulas.

Currently, some countries are considering to ban it entirely (like Denmark) and the permitted use level is very low (under 0.01%). Luckily there are plenty of products on the market with other preservative options so if you are a better safe than sorry type it's probably best to avoid it. 

Frequently Asked Questions about Methylisothiazolinone

What is methylisothiazolinone used for in cosmetics and household products?
Methylisothiazolinone is a preservative used to prevent the growth of bacteria, yeast, and mold in water-based products. It has been used in shampoos, conditioners, lotions, wipes, and some household cleaners. Because it is effective at low levels, formulators have relied on it to extend shelf life.
Is methylisothiazolinone safe to use on skin?
It can be safe for many people when used in low concentrations, but it is also a well-known cause of skin allergy and irritation. The main concern is not toxicity in the usual sense, but sensitization, meaning repeated exposure can trigger a reaction over time. People with sensitive skin or a history of eczema are more likely to notice problems.
What are the common side effects of methylisothiazolinone?
The most common side effects are skin redness, itching, burning, rash, and sometimes swelling where the product was applied. In hair-care products, reactions can also show up along the hairline, neck, or face after rinsing. If a product keeps causing symptoms, stopping it usually helps, but a persistent rash should be checked by a clinician.
Can methylisothiazolinone cause an allergic reaction?
Yes, it is one of the preservatives most often linked to contact allergy. Once someone becomes sensitized, even small amounts in rinse-off or leave-on products can trigger dermatitis. Patch testing by a dermatologist is commonly used to confirm a methylisothiazolinone allergy.
Should I avoid shampoos and conditioners with methylisothiazolinone if I have sensitive skin?
If your skin reacts easily, avoiding it is often a sensible choice, especially if you have eczema or a known preservative allergy. Shampoos and conditioners can still cause reactions because the ingredient may contact the scalp, face, neck, or hands during use. Looking for products labeled methylisothiazolinone-free can reduce the chance of irritation.

Evidence & Research on Methylisothiazolinone

Scientific Committee on Consumer Safety (SCCS) opinions 1

Products with Methylisothiazolinone (4 283 total)

Hair
Shampoos 1122 Conditioners & Masks 640 Leave-in Care 88 Styling 48 Hair Coloring 34 Hair Growth & Loss Prevention 32 Scalp Scrubs 18
Face Care
Cleansing 380 Moisturizers 164 Serums & Essences 105 Masks 77 Exfoliants & Peels 72 Face Sunscreen 56 Eye Care 34 Toning 33 Lip Balms & Scrubs 2
Body Care
Shower Gels & Bath Foams 334 Body Moisturizers 83 Body Scrubs 29 Body Sunscreen & Self-tan 21 Intimate Hygiene 8 Deodorants & Antiperspirants 6 Hair Removal 4 Anti-cellulite & Stretch Marks 3 Body Oils 2
Decorative Cosmetics
Base & Foundation 36 Eyes 11 Makeup Removers 8 Powders, Highlighters & Blush 6
Hands & Nails
Hand Creams 10 Cuticle Care 3 Nail Polish 2 Nail Treatments 1
Feet
Foot Creams 1 Foot Peels & Scrubs 1 Foot Deodorants 1

Most often found in Dove products (84 items)

Life Spa Babassu Shower Gel
Life Life Spa Babassu Shower Gel
LIFE
Life Spa Babassu Shower Gel
Simple Foaming Cleanser
Simple Simple Foaming Cleanser
SIMPLE
Simple Foaming Cleanser
Simple Kind To Skin Protecting Light Moisturizer Spf 15
Simple Simple Kind To Skin Protecting Light Moisturizer Spf 15
SIMPLE
Simple Kind To Skin Protecting Light Moisturizer Spf 15
needs Creme De Uréia 10%
needs needs Creme De Uréia 10%
NEEDS
needs Creme De Uréia 10%
needs Face Sabonete Gel Pele Normal A Mista
needs needs Face Sabonete Gel Pele Normal A Mista
NEEDS
needs Face Sabonete Gel Pele Normal A Mista
needs Facial Sabonete Gel - Pele Normal A Mista (Discontinued)
needs needs Facial Sabonete Gel - Pele Normal A Mista (Discontinued)
NEEDS
needs Facial Sabonete Gel - Pele Normal A Mista (Discontinued)
needs Hidratação Equilibrada
needs
→
needs Hidratante Facial Em Gel
needs
→
needs Hidratante Needs Vegano Dexpantenol Derma Creme Corpo Lábios E Unhas
needs
→
needs Protetor Solar Corporal FPS50 (Discontinued)
needs
→
needs Protetor Solar Facial Needs FPS 30
needs
→
needs Sabonete Esfoliante Antiacne
needs
→
All 4 283 products →
Synonyms
' Methylisothiazolinone (And)Methylisothiazolinone ＆ Methylisothiazolinone + Methylisothiazolinone +Methylisothiazolinone 2-Methyl- 4-Isothiazolin -3-One 2-Methyl-4-Isothiazolin-3-One Methylisothiažolinone Methylisothiazolinone (0.0055%) Methylisothiazolinone (2682-20-4) Methylisothiazolinone (Antimicrobial Preservative) Methylisothiazolinone (E) Methylisothiazolinone Methylisothiazolinone (Methylisothiazolinone) Methylisothiazolinone (Metilisotiazolinona) Methylisothiazolinone (Preservative)