Shampoo Without MI/MCI (Methylisothiazolinone): How to Check

A shampoo without methylisothiazolinone (MI) or methylchloroisothiazolinone (MCI) is simply one whose INCI list contains neither name, and the only way to confirm that is to read the list, because "gentle" and "preservative-free" are not regulated terms. In the EU, MI has been banned from leave-on cosmetics since 2017 and capped at 0.0015% in rinse-off products such as shampoo since 2018, so it still appears in some shampoos, and the US has no equivalent limit. Brands that leave the isothiazolinones out usually preserve with organic-acid salts such as sodium benzoate and potassium sorbate, or with phenoxyethanol-based blends. A contact allergy to MI or MCI is a medical matter: read the full INCI and patch-test with a dermatologist or allergist before relying on any product.

What MI and MCI are, and why they were in shampoo

Methylisothiazolinone and methylchloroisothiazolinone are broad-spectrum preservatives from the isothiazolinone family. They are effective against bacteria, yeasts, and molds at very low concentrations, which is exactly what a water-based product like shampoo needs to stay stable in a warm, wet bathroom. The two are often used together as a 3:1 MCI/MI blend (widely known by the trade name Kathon CG). When formulators began moving away from parabens and formaldehyde releasers in the mid-2000s, MI on its own was adopted as a replacement and permitted at concentrations far higher than in the blend.

That change is what made MI a problem. Positive patch-test rates to MI climbed in European and North American clinics through the early 2010s, and the American Contact Dermatitis Society named it Allergen of the Year for 2013. The 2013 paper by Castanedo-Tardan and Zug also noted that the standard MCI/MI patch test missed a large share of MI allergy, because the MI in that mixture is too dilute to elicit a reaction in many sensitized people. In other words, a person could test negative to the blend and still react to MI-preserved shampoo.

What the EU restricted, and why it matters outside the EU

The EU acted in two steps under Regulation (EC) No 1223/2009. First, Commission Regulation (EU) 2016/1198 removed MI from the list of preservatives allowed in leave-on products; from 12 February 2017 only compliant products could be placed on the market. Second, Commission Regulation (EU) 2017/1224 reduced the permitted MI concentration in rinse-off products from 0.01% to 0.0015%, effective for products placed on the market from 27 January 2018. The Scientific Committee on Consumer Safety had concluded that 0.0015% in rinse-off products was acceptable from the point of view of inducing new allergy, while noting the substance remained a potent sensitizer. The MCI/MI mixture had already been confined to rinse-off products at 0.0015% by Commission Regulation (EU) No 1003/2014.

Two consequences follow for a shampoo shopper. In the EU, MI and MCI are still legal in shampoo, just at a low ceiling, so an EU-compliant label can still carry either name. Outside the EU the picture is looser: the US FDA identifies both as cosmetic allergens but does not set a comparable concentration limit, and many products sold in the US still use them. Either way, a rinse-off limit is a population-level safety measure, not a guarantee for someone already sensitized; a person with a confirmed MI allergy is generally advised to avoid the ingredient entirely rather than rely on a low dose.

How to spot MI and MCI on a label

Preservatives sit near the end of an INCI list, so read all the way down. Look for Methylisothiazolinone and Methylchloroisothiazolinone; on a label they usually appear side by side as "Methylchloroisothiazolinone, Methylisothiazolinone" when the blend is used, or as "Methylisothiazolinone" alone. Older or non-EU labels sometimes use the abbreviations MI, MIT, MCI, or CMIT, or the trade names Kathon CG and Neolone. Two related isothiazolinones, benzisothiazolinone (BIT) and octylisothiazolinone (OIT), are not permitted as cosmetic preservatives in the EU but turn up in household products, paints, and some wipes; DermNet's guidance is to treat the whole group as potential cross-reactors. If the shampoo is imported or sold without a full INCI, treat the absence of information as a reason to look elsewhere, not as reassurance.

What brands use instead

Every water-based shampoo needs a preservative; the honest question is which one. The options below are the systems most commonly found in shampoos that leave the isothiazolinones out. None of them is allergen-free for every person, which is why the full INCI, not the front label, is what to check. Concentration limits are the EU maxima in Annex V of Regulation (EC) No 1223/2009.

Where Baresel fits

Baresel is one shampoo whose published INCI contains neither methylisothiazolinone nor methylchloroisothiazolinone. Its preservative system is sodium benzoate plus potassium sorbate, with citric acid holding the pH in the mildly acidic range where those two acids work, and the full list reads: Aqua/Water, Sodium Cocoyl Isethionate, Sodium Methyl Cocoyl Taurate, Sodium Cocoyl Glutamate, Glycerin, Panthenol, Sodium Chloride, Guar Hydroxypropyltrimonium Chloride, Citric Acid, Sodium Benzoate, Potassium Sorbate, Tocopherol. This formula is confirmed with the manufacturer; the label on the bottle matches it, and you hear first if anything ever changes. It is also fragrance-free and free of cocamidopropyl betaine, alkyl glucosides, and sulfates, which matters if MI is one of several things you react to. That said, benzoate and sorbate are ingredients too, and a shampoo is a cosmetic, not a treatment; check the full list against your own patch-test results with your dermatologist or allergist before use.