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Today's Chemical:


EWG Risk Score:


What is it?

Methylisothiazolinone  is a synthetic cosmetic preservative.

Why is it a risk?

  • Methylisothiazolinone is a known neurotoxin.  In 2004, the European Scientific Committee on Cosmetic Products and Non-Food Products Intended for Consumers (SCCNFP) suggested that companies limit the maximum concentration to 0.01% (100 ppm).  However, US companies are not required to follow this guideline.
  • It is known to be absorbed through skin.  A study at the Pittsburgh School of Medicine concluded that "Prolonged exposure to low levels of MIT and related compounds may have damaging consequences to the developing nervous system." 
  • Is a developmental toxin.  (Source
  • Is a known contact allergen.  (Source)

Steph's Opinion:

Although concentrations of this ingredient are typically very low in a formulation, I personally suggest avoiding this ingredient. 

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References (3)

References allow you to track sources for this article, as well as articles that were written in response to this article.

Reader Comments (45)

could it be possible that I got red and blistered skin after using bullrich's healing clay? the paste had Methylisothiazolinone as preservative.

Thu, March 10, 2011 | Unregistered CommenterIda Nowotny

It's possible. If you have a full ingredients list, post it here and I'll take a look at it for other potential irritants.

Thu, March 10, 2011 | Registered Commenter[Stephanie Greenwood]

Thanks for the info. I just realized my Seventh Generation dish soap contains this!

Wed, April 13, 2011 | Unregistered CommenterKW

Help! I have been tested and am highly allergic to Methylisothiazolinone...I have had a terrible case of excema under my arms since last fall. I am on my fifth medication, have removed all products that contain it (that I can determine) from my house, but just discovered I forgot about dish detergent! DAWN..yuk! What is a Kathon-free detergent I can purchase????

Fri, July 8, 2011 | Unregistered CommenterSusan

You might check out 7th Generation products, Susan. While they're not perfect, they at least fully disclose their ingredients, which is more than I can say for most detergents.

Let me know if you have any other questions!

Wed, July 13, 2011 | Registered Commenter[Stephanie Greenwood]

Methylisothiazolinone is a general biocide at high concentrations. Compounds like this are incorporated in paints for ship hulls to deter algae accumulation and barnacles. While not highly potent, it works by reacting with thiol groups on proteins, hence, it is not selective to any particular organism. The low concentrations in these products is the trick to make them "safe".

Sun, August 14, 2011 | Unregistered Commenterkarl fisher

I've broke out in the most terrible case of contact dermatitis on my hands due to this isothiazoline ingredient. It also has the names: Kathon, Methylcloroisothiazolinone, Methlisothiazolinone. Anything with the word isothiazolinone in it is bad if you're allergic. I had a allergy patch test done to comfirm this for me. I found it's in the Brand Especially for Baby baby wipes and It's a 10 leave in conditioner I recently started using. I'm still researching to see what else it's in so my hands can get better. This stuff sucks!!

Wed, September 7, 2011 | Unregistered CommenterHowboutnina

i was wondering what the usual concentration of
Methylisothiazolinone in Dove conditioners?
really appreciate it! :D

Mon, October 3, 2011 | Unregistered CommenterEgg

That's something that no one other than Dove would be able to tell you, and I highly doubt that they will because they consider their formulas to be "proprietary." But it wouldn't hurt to ask!

Wed, October 5, 2011 | Registered Commenter[Stephanie Greenwood]

Don't use cottonelle wipes if allergic to this ingredient. i figured it out after having a rash back there for 5 years!!!!!!! Rash went away in three days when I stopped using them.

Sat, January 28, 2012 | Unregistered Commenterrelieved

I have a severe Methlisothiazolinone allergy. I got a list of approved items from my dermatologist that is updated regularly. There are no approved dish soaps. I have to use gloves to wash dishes. What I have been disappointed by is that there are very few organics on the list. Even items where it's not listed in the ingredients are giving me issues. I have to adhere to the list specifically. It's put out by the American Contact Dermatitis Association Contact Allergen Management Program. Your dermatologist may have access to it.

Thu, February 2, 2012 | Unregistered CommenterLisa D

As far as dish soaps are concerned 7th Generation is not as clean as the company would like you to think. Full Circle is by far cleaner and won't permeate plastic like other highly perfumed dish soaps

Tue, February 21, 2012 | Unregistered CommenterCindy

The strucutre of methylisothiazolinone does not contain a benzene ring and has no structural homology with estrogen at all. Methylisothiazolinone destroys neurones by removing zinc from them thus causing a 'death cascade' leading to apoptosis.

Wed, February 29, 2012 | Unregistered CommenterJames Sharpe

I found out I was allergic to methylisothiazolinone when my company did renovations on our floor & started painting. Be warned, I foudn out too late that the preservative is also included in BEHR paint. After my face, lips & tongue swelled up to the size of a pumpkin with delightful leathery itchy skin, I went staright to the allergist, whom after about 6 months of insane testing, determined my allergy. Not only was I slathering the stuff on my face & hair everyday and wondering why my back & chest were always breaking out (rinsing Pantene out of my hair & onto my skin!), the paint incident pushed it over the top. This stuff is awful and my mom & I went on a phone crusade to determine ingredients in almost all of our household products (you can't even begin to believe how many every day products it's in! Always check labels!). I do appreciate that a lot of the companies offered me coupons or my money back, but a coupon won't help if I can't use the product to begin with. As stated above, be careful because it does come as many other names as well. Good luck.

Tue, March 6, 2012 | Unregistered CommenterEnder

@James, thanks for pointing that out; I didn't look closely enough at the chemical diagram. I saw a ring and thought benzene, but I see that the ring is completed with sulfur and nitrogen, not pure carbon, so it's not technically a benzene ring. I'll revise my article; thanks!

Mon, March 19, 2012 | Registered Commenter[Stephanie Greenwood]

I also have the dreaded allegy again the M Word, could someone tell me that if the ingrediants just have METHY does this still contain the preservitive.

Thu, March 29, 2012 | Unregistered CommenterMandy B

No, just because something has "methyl" in its name, does not necessarily mean that it's a preservative, or even that it's bad.

Thu, April 5, 2012 | Registered Commenter[Stephanie Greenwood]

Hi. I have recently started using some new "eco-friendly, non toxic products". I won't mention the brand yet! I seem to have an allergy and have seen the dishwashing liquid contains methylisothiazolinone, 5-chloro-2-methyl-isothiazol-3(2h)-one. My lips are a bit swollen, tight chest and feeling stuffy and tight in the chest. Could this be an allergy to this ingredient? I am trying to do a process of elimination to find out what is causing this allergy! Thanks!

Fri, April 6, 2012 | Unregistered CommenterKim Adie

@Kim-it's possible! I would recommend visiting an allergist/doctor to help you figure out what is causing this reaction.

Fri, April 6, 2012 | Registered Commenter[Stephanie Greenwood]

You mentioned checking out Seventh Generation products to avoid this chemical. Funny, because I decided to research methylisothiazolinone after reading it on Seventh Generation's dish liquid ingredient list! I say we all make our own soaps from herbal extracts and the like!

Sat, April 21, 2012 | Unregistered CommenterT

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