Methylisothiazolinone in Colgate Mouthwash

colgate frontEvery methylisothiazolinone allergy sufferer knows their trigger is likely to be found in cosmetics, but many, I suspect, would not guess that it can turn up in mouthwash.

Why? Well, Article 2 of the EU Cosmetics Regulation ((EC) No. 1223/2009) defines a cosmetic product as follows:

” … any substance or mixture intended to be placed in contact with the external parts of the human body (epidermis, hair system, nails, lips and external genital organs) or with the teeth and the mucous membranes of the oral cavity with a view exclusively or mainly to cleaning them, perfuming them, changing their appearance, protect­ing them, keeping them in good condition or correcting body odours”

So, mouthwashes are cosmetic products, according to this definition, and therefore the legislation governing the use of MI or MCI / MI in rinse-off / wash-off products applies.

colgate ingredients copy

Colgate Cavity Protection — the ingredients

None of this minimises my surprise at coming across methylisothiazolinone in Colgate Cavity Protection — a fluoride mouthwash commonly found on UK shelves. This product may well shield ‘teeth from cavity-causing acids’ but if you have MI allergy it will instead, I imagine, cause untold damage to your internal oral tissues that would leave you in acute pain.

The need for preservation
Any water-based preparation needs to be preserved — and water is the first ingredient in this mouthwash — and almost certainly in others.

Thankfully for the MI sufferer, most other mainstream mouthwashes do not list MI among their ingredients, but it always pays to check, and double check, and to contact manufacturers before you risk using a mouthwash — or you could be in for a particularly unpleasant shock.


MI-Free mouthwashes
No mouthwash is guaranteed to be ‘allergy safe’ for everyone, but if you struggle with high street brands — which often contain petrochemical derivatives, propylene glycol and artificial colorants — and want to explore more natural alternatives, which are free from MI and other ingredients many want or need to avoid, here are three you may like to try. If you have any further recommendations, please leave them in comments.

JASON Healthy Mouth
Several flavours of natural mouthwash, in very generously sized bottles, including ‘orange cinnamint’, ‘peppermint’ and ‘cinnamon clove’. Additionally free from parabens, SLS, petrochemicals, gluten and phthalates. Most importantly for many — they’re free from alcohol as well. 5212_Lavender_And_Myrrh_Mouthwash_Medium_1

Neal’s Yard Remedies Lavender & Myrrh Mouthwash (UK only)
Just glycerin, denatured alcohol and essential oils / botanical extracts.

s-l1000Weleda Ratanhia Mouthwash
Unusual mouthwash, which contains myrrh. Add several drops to water. Contains alcohol, and some essential oils of sage, eucalyptus and mint, for example. Claimed to be good for gums which have a tendency to bleed.

PS: Reader Donna Manuriak also recommends Tom’s of Maine mouthwashes as safe. Although I’ve not independently verified with them that they are MI-Free, you can browse the collection here.


  1. Sally McKenzie

    I’d love to know if MI is present in the preparations dentists use. I’ve had two dentists try and rebuild a broken tooth and each time I’ve been left with pain. The only answer seems to be expensive root canal treatment to remove the nerve. But I can’t help wondering if MI has been a factor all along.
    As per usual, my current dentist has zero inclination to discuss this with me, and I have no idea how I can find out.

    1. MI Free (Post author)

      That’s terrible that he or she will not even discuss. Can the dentist not even inform you what solutions / preparations he or she will be using in your treatment, so you can do your own research on the contents? When you say ‘pain’ could it have been ordinary dental work pain? MI allergy will cause rashes, broken skin, eczema – although not sure how it might affect the mouth. I’ll share this post and your comment on social media (Facebook and Twitter) to see whether anyone else may have ideas.


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