What it is
In the register’s words: “Methylisothiazolinone is the heterocyclic organic compound.”
- EU register name (INCI)
- METHYLISOTHIAZOLINONE
- CAS number
- 2682-20-4
- EC number
- 220-239-6
What the register lists it for
These are the uses the European Commission’s CosIng register lists for Methylisothiazolinone in any cosmetic, hair roles first. They say why a maker might add it, not what it does in one formula, and they aren’t a safety rating.
- Preservative
-
Stops bacteria, mold and yeast growing in the bottle. EU law allows only the preservatives on its own list for this role.
Register definition: “Exclusively or mainly intended to inhibit the development of micro-organisms in the cosmetic product. All authorised preservatives are substances in the positive list of Annex V to the Cosmetics Regulation 1223/2009.”
Where it sits on each label
US labels list ingredients from most to least, except that those at 1% or less may follow in any order. A name near the top is a large part of the formula. A label doesn’t mark where the 1% point falls, so further down, the order says little about how much is in it.
- Shampoos 1 label First five names: 0 of 1 Shampoos without it
- Clarifying shampoos 1 label First five names: 0 of 1 Clarifying shampoos without it
- Rinse-out conditioners 2 labels First five names: 0 of 2 Rinse-out conditioners without it
- Deep conditioners 2 labels First five names: 0 of 2 Deep conditioners without it
Every label, product by product (6)
- Aussie Miracle Curls Shampoo Shampoo 18th of 20 names
- Kristin Ess Deep Clean Clarifying Shampoo Clarifying shampoo 29th of 39 names
- Aussie Miracle Curls Conditioner Rinse-out conditioner 16th of 16 names
- Ouidad Curl Quencher Moisturizing Conditioner Rinse-out conditioner 24th of 24 names
- Kristin Ess Strand Strengthening Reconstructive Moisture Mask Deep conditioner 49th of 50 names
- Aussie 3 Minute Miracle Curls Deep Conditioner Deep conditioner 13th of 13 names
Each line runs from the first name on a label to the last; a dot is where this ingredient sits. Makers change formulas now and then; if the list on your bottle differs, go by your bottle.
Your next step
Other preservative ingredients on these labels
- Benzyl Alcohol 47 labels
- Dehydroacetic Acid 23 labels
- Iodopropynyl Butylcarbamate 10 labels
- Methylchloroisothiazolinone 6 labels
- Diazolidinyl Urea 5 labels
- DMDM Hydantoin 3 labels
- Propylparaben 2 labels
Updated · The name, numbers and uses come from the European Commission’s CosIng entry (CC BY 4.0); we write the uses in US spelling and put the hair ones first. The labels are each maker’s own. The order rule is the FDA’s Cosmetics Labeling Guide. All our sources are on the Sources page.