The 2026 data-driven guide to MI and MCI preservatives in Australian personal care — ACDS Allergen of the Year and EU's leave-on ban

The short version

Methylisothiazolinone (MI) and methylchloroisothiazolinone (MCI) are broad-spectrum preservatives the cosmetics industry adopted in the 1980s as a successor to parabens. Within a decade, dermatologists were diagnosing patch-test reactions to MI in record numbers — the American Contact Dermatitis Society named methylisothiazolinone its Allergen of the Year in 2013, and the EU banned MI from all leave-on cosmetic products in 2017. In Australia, MI remains permitted in both leave-on and rinse-off products under AICIS guidelines.

This guide explains what MI and MCI are, why they triggered the largest spike in contact dermatitis cases in modern cosmetic history, and which Australian-shelf categories still rely on them. For brand-by-brand scanning of MI and MCI in any AU product, use the Low Tox Gear Scanner — both compounds are flagged with severity escalation for users with eczema, contact dermatitis, MCAS, or fragrance sensitivity.

The 2013 contact-dermatitis spike — what happened

Between 2008 and 2013, dermatology patch-test clinics across Europe and North America reported a near-tripling of MI-positive patch test reactions. The European Society of Contact Dermatitis estimated that MI sensitisation rose from below 2% of patch-tested patients in 2009 to 8-10% by 2013 — making it the fastest-rising contact allergen on record.

The trigger was a 2005 industry shift. As consumer pressure mounted against parabens, formulators substituted MI (often in combination with MCI as “Kathon CG”) as the replacement preservative across shampoo, conditioner, body wash, moisturiser, wet wipes, and water-based paint. The substitution was so widespread that by 2010, MI exposure had become near-universal among consumers using standard mass-market personal care.

The ACDS named MI its Allergen of the Year in 2013. The EU’s Scientific Committee on Consumer Safety (SCCS) issued an Opinion the same year recommending immediate ban of MI in leave-on products and concentration restrictions in rinse-off.

Regulatory landscape today

EU — 2017 ban on leave-on, 2018 restriction on rinse-off. Methylisothiazolinone is prohibited in leave-on products (moisturisers, sunscreens, hair styling) and capped at 15ppm in rinse-off products. The 3:1 MCI/MI blend (“Kathon CG”) is permitted in rinse-off only at 15ppm.
UK: Follows EU restrictions post-Brexit.
Japan: MI/MCI restricted to specific rinse-off categories at concentration limits.
USA (FDA): No specific prohibition. Industry self-regulates via the Cosmetic Ingredient Review (CIR).
Australia: Permitted across leave-on and rinse-off without concentration restriction. AICIS has not aligned with the EU ban.

This is the cleanest case where AU regulatory status diverges sharply from peer markets. Products sold here that would be illegal in Berlin or restricted in Tokyo continue to use MI in leave-on formulations.

Which AU categories still rely on MI/MCI

Generalising from publicly disclosed ingredient lists on AU shelves:

Mass-market shampoo and conditioner. Many supermarket-tier ranges still use MI or MI+MCI in rinse-off formulations at concentrations near the EU 15ppm cap. Boutique/salon-grade brands have largely moved to alternative preservatives.
Wet wipes (baby wipes, hand wipes, surface wipes). MI was historically the dominant preservative; most premium baby-wipe brands (Ecoriginals, Tooshies, WaterWipes, Bamboo Bambies) reformulated by 2018. Supermarket private-label and budget wipes are inconsistent — some still use MI/MCI.
Water-based body wash. Less common since the 2017 EU action, but still appears in budget-tier formulations.
Sunscreen. Rare in modern mineral formulations but still appears in some chemical sunscreen reformulations.
Adhesives and fabric care. Some laundry products and fabric softeners use MI as an in-can preservative.

What the dermatology evidence actually shows

Patch-test data from the European Surveillance System on Contact Allergies (ESSCA, 2017-2021 cycle) consistently places MI in the top-5 cosmetic allergens by sensitisation rate:

MI sensitisation rate (patch-tested population): 7-12% across European countries, 5-9% in North America.
Cross-reactivity to MCI: 60-80% of MI-allergic patients react to MCI on patch test.
Most common presentations: hand eczema (especially in occupations using water-based products — hairdressing, painting, healthcare cleaning), face/eyelid dermatitis from leave-on cosmetics, scalp dermatitis from shampoo.
Persistence: MI-allergic patients show sustained sensitisation for years after exposure cessation. The condition is not easily “reset” by avoidance.

The mechanism: MI is a potent electrophilic sensitiser that binds covalently to skin proteins, triggering T-cell mediated delayed hypersensitivity. Concentrations as low as 200ppm (well above current EU caps) reliably sensitise naïve subjects in repeated insult patch testing.

How to identify MI and MCI on labels

Names to watch for (all are forms of the same chemistry):

Methylisothiazolinone — the primary name, INCI standard.
Methylchloroisothiazolinone — the chlorinated derivative, more allergenic.
Kathon CG — trade name for the 3:1 MCI:MI blend.
MI or MCI — sometimes abbreviated.
2-Methyl-4-isothiazolin-3-one — older chemical naming.
Methyl Isothiazolinone, 5-chloro-2-methyl-4-isothiazolin-3-one — chlorinated form.

If any of these appear in an ingredient list, the product is using MI/MCI chemistry.

What works as a safer alternative

Modern preservative-replacement strategies (used by the brands that have already reformulated):

Phenoxyethanol + ethylhexylglycerin — current industry default. Lower contact-allergen rate than MI, broad spectrum.
Sodium benzoate + potassium sorbate — food-grade preservatives, effective in acidic formulations.
Caprylyl glycol + ethylhexylglycerin — “mild” preservative system, common in “clean beauty” ranges.
Benzyl alcohol + dehydroacetic acid — newer preservative system, but benzyl alcohol is a fragrance allergen for sensitised users.
Levulinic acid + sodium levulinate — emerging plant-derived preservative.

None of these are zero-risk — every effective preservative trades off against some sensitisation potential. But all are demonstrably lower-risk than MI/MCI by patch-test rate.

How the Low Tox Gear Scanner flags MI and MCI

Our rule database covers MI and MCI under the mi_mci_preservative concern tag. Default severity is amber for general users. The rule escalates to red for users who selected: eczema, contact_dermatitis, fragrance_sensitive, MCAS, fibromyalgia, POTS, asthma, or psoriasis. The matched label text is highlighted — so when you see a product page, the specific INCI variant (Methylisothiazolinone vs Methylchloroisothiazolinone vs Kathon CG) is shown verbatim.

The eczema-safe personal care shortlist screens out both MI and MCI (alongside formaldehyde releasers, parabens, SLS, propylene glycol). 199 Australian products pass the strict-clean filter.

Best practice — what we recommend

If you patch-test positive to MI or MCI, the priority shifts to leave-on products first (moisturisers, sunscreens, hair styling). Rinse-off products are lower-priority but still worth screening. Your dermatologist will provide a specific allergen-avoidance list.
If you have eczema, contact dermatitis, or chronic dermatology referrals, eliminate MI/MCI from all daily-contact products even without a specific positive patch test. Population-level rates suggest you have meaningfully higher risk of latent sensitisation than the general population.
For asymptomatic users wanting general risk reduction, prioritise replacement in leave-on contact (moisturiser, foundation, eye products) over rinse-off. The contact time difference is order-of-magnitude.
Watch baby and children’s products especially carefully. Skin barrier development in infants is incomplete, and MI sensitisation early in life predicts lifetime sensitivity.

Related guides on Low Tox Gear

Sources

Castanedo-Tardana MP, Zug KA. Methylisothiazolinone. Dermatitis 2013;24(1):2-6. (ACDS Allergen of the Year designation.)
Schwensen JF, Friis UF, Menné T, et al. One thousand cases of severe occupational contact dermatitis. Contact Dermatitis 2013;68(5):259-268.
SCCS (Scientific Committee on Consumer Safety). Opinion on methylisothiazolinone (P94) — Submission II (Sensitisation only). SCCS/1521/13.
European Commission Regulation (EU) 2017/1224 amending Annex V to Regulation (EC) No 1223/2009 — restriction of methylisothiazolinone.
European Surveillance System on Contact Allergies (ESSCA). Annual European patch-test results, 2017-2021.
Yazar K, Boman A, Lidén C. Potent skin sensitizers in oxidative hair dye products on the Swedish market. Contact Dermatitis 2009;61(5):269-275.

This guide is educational and does not constitute medical advice. If you suspect contact dermatitis, consult a dermatologist for individualised patch testing. Last reviewed: May 2026.