Methylisothiazolinone and other isothiazolinone preservatives can appear in a number of guises.
Methylisothiazolinone (MI / MIT)
Methylchlorisothiazolinone (MCI / MCIT)
The most common expressions. Only these two will be seen on cosmetics in the EU, and almost certainly in North America and Australia too. They may also appear on other products, such as household cleaning goods and other products.
Chloromethylisothiazolinone (CMIT) (alternative for methylchloroisothiazolinone)
Octylisothiazolinone (OIT, OI)
These are most commonly seen on household cleaning products, along with MI and MCI.
And many similar variations. These are rarely seen on products, but may appear in, for example, material safety data sheets (MSDSs), such as those produced for paints. Here’s one example. It’s important if you check with producers of non-cosmetic products, that they understand that the isothiazolinone preservatives can appear under these variations. If you need to scrutinise lists of ingredients, check for the “isothiazol” string of letters, which is the typical ‘giveaway’, among all the numbers, brackets and hyphens.
(That said, some paint manufacturers refer to the preservatives as “thiazoles” or “thiazoline compounds”.)
These are branded preservative mixes which include one or more of the isothiazolinone preservatives. Again, these may be seen on an MSDS, and pose a danger because when contacting manufacturers for their MI status, unwitting customer service agents may not be aware that these represent isothiazolinone preservatives. If you can, ask for the preservation system used in the product – and look it up if necessary. This list is by no means exhaustive. In some cases, there are often many letter / number combinations following the name, denoting additional varieties, so only one or two examples of each are given.
Acticide MBS / MBR
Euxyl K 100
Fennosan IT 21
Grotan K / TK2
Kathon CG / LX / WT
Mitco CC 31/32 L
Neolone CapG / 950 / MxP
Parmetol A / DF / K
Promex Alpha / BM
Proxel AQ / PL / XL2
Special Mx 323
CAS (Chemical Abstracts Service) Numbers
These may again appear on Material Safety Data Sheets:
2682-20-4 – Methylisothiazolinone (MI)
26172-55-4 – Methylchloroisothiazolinone (MCI)
55965-84-9 – MI / MCI Blend
Other isothiazolinone CAS numbers can be viewed here.
Fragrance / Parfum
In North America (and perhaps elsewhere outside the EU), MCI can theoretically ‘hide’ in the term ‘fragrance’ or ‘parfum’, given it is one of the permitted chemicals in any blend that can be described as such. The full list of permitted compounds in fragrance can be seen here. It includes MCI (listed as 3(2H)-Isothiazolone, 5-chloro-2-methyl-).
The situation in the EU with regard to ‘parfum’ or ‘fragrance’ on labelling is not clear. The risk is probably very low. Choosing only products using natural fragrances is an almost certain safety guarantee.
Remember that fragrances can trigger allergies in their own right.
There is always the possibility that if you react to one or more of the isothiazolinones and therefore have a tendency to allergies or contact dermatitis, you may react to other ingredients, such as other preservatives, or fragrances in cosmetics and household goods. However, the following non-isothiazolinone preservatives should be safe for you:
Parabens (such as methylparaben, propylparaben)
Potassium sorbate / sorbic acid
Sodium benzoate / benzoic acid
You may also encounter some suspect ingredients may look superficially or partly like methylisothiazolinone – but are in fact fine. These ‘false enemies’ include:
Methyl sulfonyl methane
Again, you need to identify the giveaway “isothiazol” string of letters.
The fragrance compound alpha isomethyl ionone (or just isomethylionone) is also NOT related to the isothiazolinones, and should be safe. For more information about it, see our article here.