CMIT; 5-Chloro-2-Methyl-4-Isothiazolin-3-One

(in 9,233 products)

Banned by Gov or classified as a carcinogen by IARC

1. Antimicrobial Preservative - Actively kills and inhibits the growth of unwanted microorganisms which may be harmful.

2. Fragrance / Fragrance Component - Provides or enhances a particular smell or odor.

3. Preservative - Prevents and inhibits the growth of unwanted microorganisms which may be harmful

Methylchloroisothiazolinone, also referred to as MCI/MCIT/CMIT/CMI, is a preservative with antibacterial and antifungal effects within the group of isothiazolinones. MCI is effective against gram-positive and gram-negative bacteria, yeast, and fungi.

Methylchloroisothiazolinone is found in many water-based personal care products and cosmetics. Methylchloroisothiazolinone was first used in cosmetics in the 1970s. It is also used in glue production, detergents, paints, fuels, and other industrial processes.

Methylchloroisothiazolinone (MCI) is commonly used with methylisothiazolinone (MI) to form a MCI-MI mixture. The EU allows a restricted level of a MCI-MI mixture with a maximum concentration of 0.0015% in a 3:1 MCI-MI ratio as a rinse-off ingredient only.

MI has been banned for use as a leave-on product in any concentration, please see the Methylisothiazolinone page for further information.

As MCI is commonly used with MI and in the interest of consumer safety, we give a rating of 10 for MCI due to the possibility that the MI in the MCI-MI mixture might not be completely rinsed-off and the possibility that rinse-off products could be mistakenly treated as leave-on products.

As a preservative in shampoos, the Hong Kong Consumer Council has stated: "According to expert advice, applying shampoos with MIT or CMIT preservatives on open wound could lead to a higher chance of adverse discomfort reaction."

Nevertheless, methylchloroisothiazolinone remains as an approved ingredient in CosIng Annex 5. 1Source hypothesizes that either those two agencies rate ingredients independently of each other, or that the CosIng Annex 5 has not yet been updated as of 2018.

1Source understands the confusion for consumers, but in the interest of consumer safety, 1Source gives a rating based on the agency with the harshest rating of the ingredient in question.

1. PubChem: https://pubchem.ncbi.nlm.nih.gov/compound/33344

2. Contact dermatitis to methylisothiazolinone (An Bras Dermatol. 2015 Nov-Dec; 90(6): 912–914. doi: 10.1590/abd1806-4841.20153992)

3. Prevalence of methylchloroisothiazolinone and methylisothiazolinone contact allergy in facial dermatitis: a single centre Irish study. (J Eur Acad Dermatol Venereol. 2016 Jan;30(1):60-2. doi: 10.1111/jdv.12956. Epub 2015 Jan 26.)

1. CANADA INGREDIENT HOTLIST, List of Ingredients that are Restricted for Use in Cosmetic Products [2019]

- Methylisothiazolinone

2. Japan - Ministry of Health, Labour and Welfare - Restricted Ingredients

- Methylchloro isothiazolinone and methyl isothiazolinone solution

3. US FDA Food Additives Status List [2018]

- Indirect Additives used in Food Contact Substances

- §175.105 / §175.300 / §175.320 / §176.170

4. Hong Kong Consumer Council 2017-2018 Annual Report

- Report: Improving Product Quality and Safety, p29

5. Hong Kong Consumer Council

- CMIT (methylchloroisothiazolinone) - Preservative Irritant

6. Hong Kong Consumer Council 2019-2020 Annual Report

- Report: Improving Product Quality and Safety, p30

7. EU CosIng Annex V, PRESERVATIVES ALLOWED IN COSMETIC PRODUCTS [2017]

- Ref: V/57

8. International Fragrance Association Transparency List [2015]

9. EU Commission Regulation

- No. 1003/2014