Some of you might be wondering, what in the world is the ingredient methylisothiazolinone?? Other readers might be excited to learn more about methylisothiazolinone!

Either way, this is an important post for anyone who might want to learn more about specific ingredients found in home and skincare products.

Today, we will be sharing with you what the ingredient methylisothiazolinone is plus why it is used.

Instead of myths, hearsay, or word of mouth, we are basing today’s post on scientific research from experts.

Science and research are important when it comes to examining products!

Let’s get started.

What You Need To Know About The Ingredient Methylisothiazolinone

This post is about what and why the ingredient methylisothiazolinone is used. After receiving some disturbing comments from a few people (not readers of Chemistry Cachet), I wanted to add this in here in case there is confusion.

Why Is Chemistry Cachet Writing This Type Of Post?

A few years ago, I had a reader ask if I was familiar with MIT (methylisothiazolinone). This reader told me she was having some issues with a few clients of hers (she cleaned homes professionally), and this ingredient came up. Her clients had a sensitivity to it, but she was not familiar with it.

Over the last few years, I have received other emails from readers wondering why preservatives are used in store-bought products. So, this post is informational, and for you to see why preservatives are used at all in products. It is also to share with you some information about this particular ingredient, methylisothiazolinone, because it has become one of the most widely used preservatives in cleaning and skincare. Believe it or not, ALL store-bought products contain preservatives because they have to meet EPA and other governmental standards for shelf-life. Without preservatives, products go bad and can be dangerous to your health.

Homemade cleaners are awesome, and they help to LIMIT unnecessary ingredients. The drawback to homemade cleaners or products is they are not formulated for specific things. So, it is a balance you need to take into consideration. You can visit this recent post about cleaning vs disinfecting to get more of an understanding to this subject. 

FAQs Regarding Our Post on MIT

After this blog post was published, there was a misunderstanding about the purpose of this article. Before you continue on reading this, please go through these questions and answers. Chemistry Cachet is about sharing science based information. We do not endorse particular ingredients, products, or companies. Instead, we want to share with you the science about how things work. Due to a few recent emails, I would like to start with some FAQs.

Is this post sponsored? – This post is not sponsored with or for anyone or company. This was for our readers who have asked about this particular ingredient. 

Are you supporting and encouraging this ingredient? – No, this post has nothing to do with support or encouragement. This post is to share with you the WHAT and WHY methylisothiazolinone is used (along with other preservatives). Again, this is informational. If you are wanting to make a statement or anything like this, please visit the EPA, CDC, or local governmental website. 

Is this a promotional post? – No.

Do you work with this ingredient? -I have used products in the past that contain this ingredient…you might be surprised that many products do. This is why we are writing this post, so you can have information.

Are you defending the use of this product? – This is another NO! I have no bearing on this ingredient nor do I work for a company that uses this product. Chemistry Cachet is a lifestyle blog, so we share information.

I really urge anyone reading this to send information to the EPA or another organization with concerns. I don’t work with this or have any bearing on the laws. When this article was published, there were some people who stumbled upon it thinking Chemistry Cachet was a laboratory or affiliated with governmental laws. We are not any of those things.

We have also had emails asking why we use this ingredient  I would like to remind anyone reading this, we are not a manufacturer or government website  Please reach out to a manufacturer or the EPA with concerns like this.

What Exactly is Methylisothiazolinone ?

Now that you have read through the FAQS, I want to share with you WHAT MIT is plus why it would be used.

Methylisothiazolinone (also known as MIT) is a common preservative found in home and skincare products. It inhibits growth of microorganisms during storage and use.  It has the molecular formula: C₄H₅NOS.

MIT meets the EPA’s safer choice ingredient list. The EPA sets standards for products like the FDA does for food and drug products. Just like the CDC is the governing authority for disinfecting and protecting against virus and bacteria in commercial areas. 

Why is Methylisothiazolinone used in cosmetic and personal care products?

According to cosmeticsinfo.org, Methylisothiazolinone (MIT) is often used as a mixture with Methylchloroisothiazolinone (MCI). They also mention, “Any product that contains water is particularly susceptible to being spoiled by microbial growth, causing problems such as discoloration, unpleasant odors or breakdown. Under certain conditions, microorganisms can even grow to potentially harmful levels. Preservatives are designed to help prevent these problems.”

This wording is the key to why a preservative is used in personal care and cosmetics. Without a preservative, many things can occur to the products you are purchasing. It can spoil, and microorganisms can grow to a harmful level. It can also cause your product not to function as it should. These are added to insure the product you purchase is working properly plus safe to keep using once it is open.

You can follow this link to learn more about why preservatives are used.

With the standards the government has set into place, store-bought products must meet requirements for shelf-life, safety, and performance. This is why everything you purchase at the store for cleaning or skincare will contain a preservative. Even green, organic type of products contain preservatives like Seventh Generation which is a popular green cleaner (They use MIT also).

 Methylisothiazolinone in Products

With all this being said, we are going to focus more on the cleaning aspect of the ingredient methylisothiazolinone. While we do talk about skincare products on Chemistry Cachet, most of the products we recommend do not contain MIT or the MCI mentioned above. If you turn your skincare product over and look at the ingredients, you can see if your product contains these preservatives. You will more than likely see it in body washes and shampoos.

But for our post, we are narrowing down on cleaning.

Cleaning products, to us, are a little different. You want your cleaning products to be safe, but you also want them to work!

Since we talk about DIY cleaners all the time on Chemistry Cachet, you will notice they are all made in very small batches. In fact, many of our DIY cleaners are meant to be used within one -two uses. Why? Because they don’t contain preservatives. This means they are only effective for a short amount of time.

When you purchase a cleaning product at the store, they must be formulated for long-term use and safety. Which leads us back into the preservative topic.

Regardless of what product you buy at the store, it will contain a preservative. Organic, green, regular, plant based, or whatever it might be, it will need a preservative for storing and safety.

The Safety of Methylisothiazolinone

It is not a carcinogen and it is has no developmental or reproductive toxicity according to the EWG.

Why is there controversy on it then? Because of its use in cosmetics, and it winning Allergen of the Year in 2013! After it received this awareness, there were many testing procedures done to see what results were in people who had skin reactions to it.  You can head over to the Dermatitis Journal for the research they conducted on this. The findings were” After a 7- to 15-day rest period, subjects were challenged on a virgin site for 24 hours with the same induction concentration. Only 1 subject in each of the 400-ppm and 500-ppm dose groups had an erythema response. The authors concluded that up to a concentration of 600 ppm, MI is not a dermal sensitizer.”

Most people do not have a sensitivity to this ingredient, even with repeat exposure as you can read in the article above. I urge everyone to read through the studies on this. If you suspect you might have a skin reaction to this, it is important to call your doctor. 

The Safety Of Methylisothiazolinone in Products

To complete this post, we wanted to include some additional safety information from top manufacturers. We reached out to scientists and toxicologists at P&G because they have some of the top researchers in the country with the ability for adequate testing. Chemistry Cachet trusts companies like this to perform proper research on products for consumers. 

If you head to this document from the Dermatitis Journal, you can read more research and history of MIT. If you read the document, you can see there are two different preservatives used: 1) MIT alone, and 2) the MCI/MI combination (i.e. Kathon), which is a preservative itself and not just an addition of two chemicals.

P&G wanted to emphasize they’ve never used MIT or Kathon in anything leave-on because they have never considered it safe at that level for that type of exposure. However, many people with this allergy developed it from past exposure to MIT or Kathon in other (non-P&G) leave-on products. Once people are sensitized by either MIT or Kathon, then subsequent contact to even very small amounts of MIT in a product could cause an allergic reaction in those people. Said another way, the amount of MIT in any P&G product is not high enough to trigger skin sensitization (or skin allergy) in healthy people, but for those who are already affected, it could trigger contact dermatitis reactions (or allergic reactions).

For clarity, MIT is the preservative in Dawn products, and it is formulated well below the critical threshold for sensitization. Other P&G Home Care products, such as Febreze and Cascade Gel, use Benzisothiazolinone (BIT) as the preservative. Although the name sounds similar, it is structurally different and is highly unlikely to cause an allergic reaction in people with an MIT or Kathon allergy.

This was a very good point sent from P&G. If people have developed an allergy from PAST exposures, subsequent contact to small amounts of MIT can cause a reaction. 

So if you think you might be sensitive to this ingredient or you have used leave-on products before that contained MIT, check with your doctor about skin issues.

In conclusion, what is this post about?

We are talking about WHAT this ingredient is plus why companies have used it. Be sure to read through the links we to the Dermatitis Journal for the in-depth studies they did. If you need further information about any issues with it, please visit the EPA. This post is not to be controversial, but to explain what this ingredient is plus it is it used for!

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