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  • Writer's pictureThe Pink Elephant Lady

Chemical of the Day: Methylchloroisothiazolinone

This one usually takes the cake for longest ingredient name you'll find on a product label. But before we dive into exactly what it is, let's talk about the mantra "if you can't pronounce it, don't eat it". Why? Well, methylchloroisothiazolinone has a lot of syllables, and it sure SOUNDS scary. But let's explore if whether or not you can pronounce an ingredient has anything to do with its safety. Take a look at the picture below.

Yes, that's an all-natural, non-GMO banana, and none of those components are insecticides, pesticides, or other contaminants. They're just all the things that make a banana - well, a banana! I don't know about you, but there sure are a lot of things I can't pronounce on that list of banana ingredients. The point is, whether or not we can pronounce something has nothing whatsoever to do with whether or not it is safe.

Now that we've gotten the idea out of the way that something must be dangerous if we can't pronounce it, let's go back to methylchloroisothiazolinone. Methylchloroisothiazolinone is a synthetic preservative used in personal care products and cleaning products. It's in Seventh Generation products and in Target's line of Method products. It's in many grocery store shampoos, and it's in Aveda's 'Damage Remedy' shampoo. (I bring this up because if you're buying any of these brands because they're 'natural', you'd be mistaken). As a matter of fact, Seventh Generation settled a class action lawsuit back in 2016 over its labeling of products as “natural,” “non-toxic,” and/or “hypoallergenic", when in fact the products contained synthetic ingredients and allergens like benzisothiazolinone (‘BIT’), methylisothiazolinone (‘MIT’), laureth-6, sodium lauryl sulfate, lauramine oxide, sodium citrate, and/or synthetic glycerin.

Methylchloroisothiazolinone (or MIT) is part of a group of chemicals known as isothiazolinones, the most potent allergens on the consumer market “We are in the midst of an outbreak of allergy to a preservative [methylisothiazolinone] which we have not seen before in terms of scale in our lifetime…. I would ask the cosmetic industry not to wait for legislation but to…address the problem before the situation gets worse,” stated John McFadden, FRCP, consultant dermatologist at St. John’s Institution of Dermatology in London, in a 2013 article in The Telegraph. And in 2013, MIT had the dubious distinction of being named 'Allergen of the Year' by the American Contact Dermatitis Society.

Apparently, just because you haven't ever had a reaction to it yet, doesn't mean you never will. According to the medical journal The Dermatologist, "Exposure to a contact allergen can be for days to years before subsequent sensitization occurs and ACD (contact dermatitis) is clinically apparent. With every exposure, there is the possibility that the immune system reaches a threshold and subsequent exposure results in eliciting a cutaneous (skin) response." Basically what that means is every exposure increases your risk of having a reaction, until one day you've passed crossed a certain threshold.

In 2013, the European cosmetic industry voluntarily agreed to remove MIT from leave-on skin products (including wet-wipes). Regulation in the United States has yet to follow. The Cosmetic Ingredient Review expert panel (an organization funded by the Personal Care Products Council, the lobbying/trade association of the personal care products industry) maintains their opinion that methylchloroisothiazolinone “is safe for use in rinse-off cosmetic products at concentrations up to 100 ppm".


Methylchloroisothiazolinone may be a strong skin irritant, but it's also a very effective preservative. In order to be shelf-stable and safe, products with water in them need preservatives. As a rule, water-based creations will have a much shorter shelf-life than oil and butter-based ones, because water breeds life! This is why salves and balms tend to have much longer stability than lotions and creams. But, oils in products can oxidize and go rancid. Not good.

If you're making stuff at home for your own personal use and plan on using it up fairly quickly, you may not need preservatives. But a product being shipped to a store where it may then sit on a shelf for six months? Different story. In 2014, 4,500 units of lotion products from the Kutol company were recalled in the U.S. due to contamination with bacteria belonging to the pseudomanas genus — a pathogen that can cause inflammation, pneumonia, blood infections and even sepsis, a potentially fatal whole-body inflammation. Yikes! And Vogue International pulled over 200,000 bottles of OGX Biotin and Collagen Conditioner due to the presence of Burkholderia cepacia. The bacteria can cause life-threatening respiratory infections for individuals with compromised immune systems. And those are not the only examples, of course (read more here:

As consumers became more concerned about parabens (also very effective preservatives), many manufacturers stopped using parabens altogether, and the isothiazolinone family of preservatives became more commmon in products. The explosion in demand for methylisothiazolinone directly translated into a significant increase of the prevalence of skin sensitization to this allergen in the general population. (I won't get into too much detail here about parabens - we'll save that for another blog post!)


As manufacturers, we want to avoid using harsh ingredients (after all, I use my products myself!), but we also need to keep our customers safe from dangerous contaminants. "Just use coconut oil/Vitamin E/essential oils, then!" Hmmmm...not necessarily. Many natural ingredients commonly called 'preservatives' by bloggers and DIY gurus are not truly preservatives but more accurately antioxidants. For example, vitamin E and grapefruit seed extract are antioxidants which can keep oils and fats in products from going rancid, but are not very effective against fungi and bacteria.

CONCLUSIONS Avoid leave-on products (facial creams, lotions) that contain methylchloroisothiazolinone, especially if you have sensitive skin. Cleaning products with methylchloroisothiazolinone, which do not have extensive contact time with the skin, are probably safe. However, if you or someone in your household has eczema or other chronic skin problems, I'd probably try to avoid methylchloroisothiazolinone altogether. I don't know that I'd trust a manufacturer or handcrafter selling water-based products with no preservatives added.

The potential for skin irritation needs to be balanced with the need for products to be preserved safely. Balancing consumer concerns with what we know to be true about the importance of effective preservatives can be challenging. Handcrafted shampoos, rinses, and creams will usually not have the same shelf-life as mass-produced products. But, not all consumers want to or are able to make their own personal care and cleaning products, thus the market for shelf-stable products is not going away anytime soon. And, according to the Campaign for Safe Cosmetics, as long as you are not allergic, methylchloroisothiazolinone is among the safer preservatives with regard to long-term chronic health effects.


Aljazeera: Bacterial Contamination in Cosmetics Eludes Public Eye.

The Dermatologist: Update on Isothiazolinones.

Dermatology News: Methylchloroisothiazolinone Named Allergen of the Year.

Campaign for Safe Cosmetics: Methylisothiazolinone and Methylchloroisothiazolinone

#ChemicaloftheDay #cleaningproducts #productsafety

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