​Ingredient Spotlight: Methylisothiazolinone

In this article, we take a look at Methylisothiazolinone - an ingredient commonly used in personal care products and more.

What is Methylisothiazolinone?

Methylisothiazolinone - also known as MI - is a synthetic preservative used in many consumer products, including cosmetics, pharmaceutical products and household cleansers, as well as industrial products and settings like jet fuels, printing inks and cooling tower water.

Methylisothiazolinone

What are some specific examples of products containing Methylisothiazolinone?

You can find MI in makeup items like foundation, eye shadow and mascara, as well as personal care items like moisturisers, sunscreen, lotions, gels, mouth wash, shampoos, soaps, body wash and wet wipes, including baby wipes. It’s also used in some over-the-counter and prescription medicines, along with household cleaning products, laundry detergents, polishes, adhesives, pesticides and so on. Yes, it’s just about everywhere!

What are the safety concerns surrounding Methylisothiazolinone?

Two of the main concerns surrounding MI are:

• Neurotoxicity – lab studies on the brain cells of mammals suggest that MI may be neurotoxic.
• Skin sensitisation and allergies – MI has exhibited skin sensitisation effects and may also cause systemic acute toxicity and local effects such as eczema and contact allergy reactions.

Is Methylisothiazolinone bad for humans?

As far as allergic reactions are concerned, the increase in the number of cases of allergic contact dermatitis has been quite dramatic in recent years. In particular:

• In 2011, Drs Jennifer Cahill and Rosemary Nixon (Dermatologists with the Skin and Cancer Foundation Inc.) began including MI in their baseline patch test series for allergies, following European reports of increasing cases of MI contact allergy.

The rate of positive test reactions to MI in 2011 was 3.5%, increasing to 8.4% in 2012 and increasing further in 2013 to 11.3%.

The doctors declared in 2013 that “MI is now the most common cause of allergic contact dermatitis in our patient population.”

Dr Cahill also wrote that “interestingly it is parents using baby wipes on their children who are presenting with hand dermatitis, although it is likely that allergic contact dermatitis involving the groin in children may not be diagnosed accurately.”

• The allergic reaction of people to MI has been described as an ‘epidemic’ and the American Dermatitis Society named MI ‘Allergen of the Year’ in 2013.
• According to Safe Work Australia, MI is recommended for classification as hazardous with the risk phrase ‘Causes burns’ . MI has also been recommended for classification as highly corrosive and is expected to be severely damaging to eyes in its undiluted form.
• In Australia, the Occupational Dermatology Research and Educational Centre has spoken to the ACCC addressing the effects of MI as a consumer safety issue. They have also alerted the National Industrial Chemicals Notification and Assessment Scheme (NICNAS).

Is Methylisothiazolinone related to Methylchloroisothiazolinone?

Methylchloroisothiazolinone - also known as MCI - is in the same group of preservatives (called isothiazolinones) as MI. Historically,  MI has often been combined with MCI in a blend of 1:3 (1 part MI to 3 parts MCI). This is because MCI is also a strong skin sensitiser and is not allowed to be used in cosmetics on its own – only with the MI blend in the aforementioned ratio. Since the early 2000's, however, MI has been allowed as a standalone preservative for industrial products. Since 2005, this has also been the case for cosmetics.

Is the use of Methylisothiazolinone regulated by Governments?

Trying to determine the exact status regarding Government regulation of MI in various parts of the world can be confusing, mainly because there have been so many concerns raised as to its dangers and so many proposals to amend the generally accepted maximum concentrations in both rinse-off and leave-on cosmetics of 100 ppm (parts per million) or 0.01%. Interestingly, in 2018, Cosmetics Europe recommended discontinuing the use of MI in cosmetics altogether.

Here's some information we found regarding Government regulation of MI around the world:

• China - the limit level of MI is still 0.01% in cosmetics. The mixture of MCI and MI is only available to rinse-off products with the limit level of 0.0015% in a ratio 3:1 of the two substances. For rinse-off products, the mixture of MCI and MI could not be used with additional MI in cosmetics.
• Japan - MI is restricted to a maximum of 0.01% in both wash-off and leave-on cosmetics.Canada - according to healthline.com, MCI is only permitted in combination with MI. If the MCI/MI combination is used in a formulation with MI alone, the total cumulative concentration of MCI/MI must not exceed 0.0015%. Canada, MCI/MI is permitted for rinse-off products and not permitted for leave-in products.
• European Union - in 2016 leave-on cosmetic products containing the combination MI/MCI were banned from the European market. In 2017 MI used on its own was banned in leave-on cosmetic products. In 2017 the maximum concentration of MI allowed in rinse-off products was reduced to 0.0015% (15 parts per million).
• USA - the use of MI in wash-off and leave-on cosmetics is restricted to a maximum concentration of 0.01%.
• Australia - the allowed concentration of MI in rinse-off cosmetic preparations or therapeutic goods intended for topical rinse-off application is 0.01% or less. In other preparations not intended for direct application to the skin, the maximum concentration remains at 0.1%.

Conclusions and take-aways regarding Methylisothiazolinone

There is so much information available online about both MI and MCI and all the safety concerns and different regulations around the world. It can be quite confusing but you should do your own research if you are concerned about this ingredient.

From the information we found, it appears that:

• current clinical data indicate that 100 ppm (0.01%) MI in cosmetic products (although allowed) may not be safe for the consumer
• for leave-on cosmetic products (including 'wet wipes'), no safe concentrations of MI for induction of contact allergy or elicitation have been adequately demonstrated
• for rinse-off cosmetic products, a concentration of 15 ppm (0.0015%) MI is considered safe for the consumer from the view of induction of contact allergy - however, no information is available on elicitation
• MI/MCI would never be allowed in certified organic products
• baby wipes featured quite a lot in our research as being of major concern, yet even the ones with label claims of 'natural', 'organic' or 'gentle' often contain MI or MI/MCI so beware
• preservatives are necessary in products containing water - no-one wants bacteria or mold in their cosmetics - that would definitely be unsafe, however, finding the ideal preservative that is effective and completely safe for humans at the same time is a difficult task

According to medicaldialogues.in, isothiazolinone allergy is decreasing in Europe but increasing in North America, mostly likely due to the more stringent and earlier Government regulation of MI in Europe.

Sources:
EWG’s Skin Deep Cosmetics Database.
Therapeutic Goods Administration (TGA)
madesafe.org
healthline.com

Disclaimer:
The author is not a health professional. Any information or advice in this article is of a general nature only and taken from the author's own research of information readily available online. Nothing in this article is intended to diagnose, treat, cure or prevent any disease. For medical advice regarding your own personal circumstances, it is recommended that you contact your GP or other healthcare professional