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Cosmetics: Methylisothiazolinone The Ingredient You Should Be Wary Of

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Although its name is difficult to pronounce, methylisothiazolinone has become very common in hygiene and beauty products.

Why? Simply because it is the trendy conservative, the one who officially replaced parabens. The problem is, it’s not really better.

In fact, it may even be worse… I suggest taking stock at the situation in order to avoid using this ingredient.

From methylisothiazolinone to reality

Methylisothiazolinone, commonly referred to as “MIT or MI”, has gained a strange reputation.

Already in 2013, French dermatologists publicly decried this ingredient as one of the most likely to cause skin irritation.

Not only is it together with its “fellows” (ingredients that end in “-isothiazolinone”) very irritating, but some studies even attribute neurotoxic effects to them.

Scientists have conducted laboratory research on rat brains. They found that brief exposure to methylisothiazolinone caused damage to nerve cells but also to vision cells [1].

Despite these warning signs, methylisothiazolinone is present in several so-called “rinsed-off” products, such as shampoos, shower gels and washing gels.

I even found it in a baby washing gel that said it was “very soft”.

But what exactly is MIT?

In the preservative family, methylisothiazolinone is a powerful biocidal agent. It is capable of killing harmful microorganisms in a product or limiting their proliferation.

Contrary to what one might think, it is not new.

It just came back in force when manufacturers looked for alternatives to parabens, which are too easily identified on labels by health-conscious consumers.

Initially, methylisothiazolinone, still unknown to the general public, is more easily overlooked.

In addition, MIT has surrounded itself with very close cousins, all the other “isothiazolinones”, who fulfil more or less the same functions, but also have the same harmful effects….

It is therefore difficult to identify its presence on the label among the complete list of ingredients.

Why is MIT used?

Cosmetics manufacturers will tell you: “Don’t panic, we use a very little amount of methylisothiazolinone.” Which is expressly recommended by the authorities, as this preservative has such an irritating potential.

And they will add, “It is used in rinse-off products… You will agree that it is important to find a conservation method for cosmetics that contain a lot of water. As parabens are no longer welcome, the MIT is essential. It is not too expensive and very effective. »

However, my question has been the same for several years: why not use other softer and less controversial preservatives?

Because there are a few: they have been used for several years by certified organic or natural brands.

But they are more expensive and a little more complex to formulate.

Better consume in 4 steps:

  1. Before buying a cosmetic product, always read the ingredient list. It must appear on the packaging of the product, even if it is sometimes a little hidden.
  2. Read the complicated words and try to avoid the following ones, which refer to controversial conservatives. Be careful, there are many: BHT, BHA, EDTA, triclosan, phenoxyethanol, benzophenone, -paraben-, … and methyl and/or other/-isothiazolinone!
  3. If the exercise is too difficult, trust a recognized organic label or use an application on your smartphone (Clean Beauty, Think Dirty,…).
  4. Not convinced? Simply try to wash your body and hair with the least processed products possible: rhassoul clay, eggs, lightly vinegared water, floral water, or of course real traditional cold-processed soap.

If you have other alternatives to avoid controversial ingredients, share them here with us.


[1] Shen Du et al., “In Vitro Neurotoxicity of Methylisothiazolinone, a Commonly Used Industrial and Household Biocide, Proceeds via a Zinc and Extracellular Signal-Regulated Kinase Mitogen-Activated Protein Kinase-Dependent Pathway”, Journal of Neuroscience, September 1, 2002, 22(17): 7408-7416 et Spawn A. et al., “Abnormal visual processing and increased seizure susceptibility result from developmental exposure to the biocide methylisothiazolinone”, Neuroscience, 2012 March 15;205:194-204.


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