Ingredient Watch List: Methylisothiazolinone, the Toxic Ingredient That Could Cause Nerve Damage

Man helping himself to a dollop of antibacterial soap, close up of hands

Also called MIT, this ingredient is often found in antibacterial products.

Unlike some synthetic chemicals, however, this one isn't just a mild skin irritant. A recent study found the chemical may actually be linked to nerve damage, and it's also known to be toxic in several other ways.

Let's figure out how to avoid this one!

What is MIT?

This ingredient is a powerful biocide. That means it's a chemical substance that can control or kill harmful microorganisms. It works well as a preservative in products like shampoo and body care products, helping them to last a long time on the shelf and in your bathroom cabinets without becoming contaminated with unwanted bugs, bacteria, and fungi.

MIT belongs to a group of similar compounds called “isothiazolinones,” which also include the following chemicals:

  • Chloromethylisothiazolinone (CMIT)
  • Benzisothiazolinone (BIT)
  • Octylisothiazolinone (OIT)
  • Dichlorooctylisothiazolinone (DCOIT)

You'll find MIT and chemicals like it at low concentrations in “rinse-off” products like shampoos, conditioners, hair colors, body washes, laundry detergents, liquid hand soaps, bubble bath, hand dishwashing soaps, and shampoo/conditioner combinations.

What are the Concerns?

The biggest concern with this ingredient came to light when researchers conducted two recent laboratory studies on rat brain cells, and found that MIT caused damage to those cells. The researchers stated, “a brief exposure to methylisothiazolinone, a widely used industrial and household biocide, is highly toxic to cultured neurons….” The scientists went on to state that these toxic effects had been reported previously, and because of their widespread use, the consequences of chronic human exposure need to be evaluated. What was most concerning about this study was that the exposure was only 10 minutes long.

What did the cosmetic industry say about this? The Cosmetic, Toiletry, and Fragrance Association (CFTA) issued a response stating that MIT is safe as it is used in cosmetic formulas because the exposure is so low. Indeed, in 2004, the European Scientific Committee on Cosmetic Products and Non-Food Products Intended for Consumers (SCCNFP) suggested that companies limit the maximum concentration of MIT to 0.01 percent, or 100 parts per million (ppm). U.S. companies, however, are not required to follow this guideline.

Other Concerns

Another study found that exposure to MIT caused dermatitis, while a recent 2012 study found that brief exposure to MIT is toxic in low concentrations during neural development, increasing the risk of seizures and visual abnormalities. “Our findings,” stated the researchers, “combined with the fact that the long-term neurological impacts of environmental exposure to MIT have not been determined, suggest a need for a closer evaluation of the safety of MIT in commercial and industrial products.”

The Environmental Working Group (EWG) also states that MIT is a skin sensitizer and irritant, which means that it can cause contact allergies.

Bottom Line

Cosmetic companies defend their use of this ingredient by stating that they use very low amounts, at around 15 ppm. They further claim that because the ingredient is in “rinse-off” products, any dangerous or toxic effects are washed down the drain. Meanwhile, you have a bacteria-free formula that lasts a long time on your shelf.

I don't know about you, but that doesn't really make me feel any better about using this stuff. The scientists themselves are saying we need more research to determine safety—in my book, that means, “stay away until we know more!”

Here's another quote from the first neurotoxic study I mentioned:

“Unfortunately, we have little or no information about the potential negative impact on the brain for many commonly used substances….The long-term consequences of low-level chronic exposure to isothiazolinones on the central nervous system have not been investigated.”

Besides, we don't need these toxic, skin damaging preservatives in our products.

Discover some of our favorite organic products with our most popular list!

Do you avoid MIT in your products?

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Photo courtesy Naturally You Skin Care via Flickr.com.

Sources
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, http://www.jneurosci.org/content/22/17/7408.abstract.

http://www.jneurosci.org/content/22/17/7408.full.pdf.

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, http://www.ncbi.nlm.nih.gov/pubmed/22245758.

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  1. Bernice Sachiko says

    My Dove product got this ingredient. I think I won’t use this product ever again. No wonder it feels weird why the skin on my neck tend to be more itchy, irritated and sensitized than usual to actually trigger Eczema. ????

  2. Tom Kretzmer says

    I developed a severe sensitivity to this preservative, to the point where if I touch a handle used by someone who used soap with this preservative, I develop deep painful blisters that linger for weeks where that contact occurred. Took me years to figure out that these chemicals were causing it. For those without the allergy, it’s a superb preservative. But for those of us who have become allergic, it’s as if half the world is covered in poison ivy.

  3. Jmh says

    I underwent allergy testing because of continual body rashes. Was allergic to this and quarternium-15 and some other formaldehyde releasers, which was in my new, reformulated body lotion.

  4. Mary S says

    I saw a post in Branch Basics and now here. It’s in my dishwashing liquid that I thought was a safe brand. I wonder if the issues with my skin under my eyes are coming from this? Jeez! It never ends. I thought I had everything cleared out of my house. Now I’ll look at the automatic dishwasher detergent and my laundry detergent. I may have to go back to making my own again. 🙁 Thanks for sharing this!

  5. Ginger says

    I am not sure if one or both of the following points were mentioned in the article above, but I read a newspaper article from the UK that was written in 2017 that said that
    1) the EU has already banned methylisothiazolinone from leave-on products (for example, skin lotions and cosmetics), and
    2) starting sometime in 2018, EU regulations will come into force that will require such a low maximum of methylisothiazolinone to be in rinse-off products (for example, shampoos and laundry detergents) that most producers won’t even want to put MI in their rinse-off products because the low maximum level will not be enough to allow it to function as a reliable preservative.
    Therefore, I wonder if people living in the US might be able to import personal care products that are made for sale in the European Union (manufactured in 2018 and beyond, so that they will have to fulfill both of the regulations described above) and thereby avoid methylisothiazolinone?
    I have read that certain international brands have MI in their American products but not in their British products (such as Ecover laundry detergent).

  6. Glenn says

    I have switched my body wash, shampoo, and conditioner to brands that do not include MIT or any of its relatives. One thing we do not need is a substance with neurotoxic properties being used on our scalps which is right next to our brain. I’m guessing the rise in brain cancer over the last 50 years may be attributed in part to exposure to MIT. Studies in the next few years should hopefully shed more light on the effects of this chemical. Otherwise, I would steer clear. Just read the labels before you buy any liquids, cream or lotions you put on your skin or head.

  7. Leigh says

    I, too, had a patch test after severe eye problems. MIT was an irritant for me along with paraben, proplis, cobalt chloride, glyceryl thioglycolate and glutaraldehyde. ALL in products uses around the house. I dumped all products I had been using (some well known, expensive body creams) and use only what is on my list including toothpastes. Vinegar, baking soda and other products that do not have these ingredients in them is what I use now. I don’t even use soap in public bathrooms because I don’t know what is in them.

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