Celeiq

Ingredient guide · reviewed 2026-10-10

Methylisothiazolinone (MI / MIT) in skincare

Methylisothiazolinone (MI, also written MIT) is a preservative that caused an unusually high rate of skin allergy in Europe in the early 2010s. The EU now bans it in leave-on cosmetics and limits it to 0.0015% in rinse-off products. Not everyone who uses it becomes allergic, but people who are allergic can react to small amounts.

What is MI and why is it used?

MI is a preservative, added to help keep products from spoiling.7 In the EU it's now limited to rinse-off products, such as shampoos and body washes.5 It isn't only found in cosmetics. The EU's Scientific Committee on Consumer Safety (SCCS) has noted that MI is also widely used in other consumer products, such as detergents and paints.1 MI also comes in a mixture with a related preservative, methylchloroisothiazolinone (MCI). EU law regulates that mixture separately, also limits it to rinse-off products, and doesn't allow MI and the MCI/MI mixture to be used together in the same product.5 If you're checking labels, it's worth knowing both names.

What happened with MI allergy?

MI was originally allowed in EU cosmetics at up to 0.01% (100 ppm).3 Dermatology clinics then recorded a sharp rise in allergic reactions. In Belgium, 6.0% of patients patch tested in 2012 reacted to MI, rising to 7.2% in 2013. A French network reported 1.5% in 2010, 3.3% in 2011 and 5.6% in 2012. The SCCS described the increase as having reached "epidemic proportions" in some countries, with new cases even in children aged one to two.2 The committee also concluded that safety assessments based on predictive lab tests had failed to protect consumers from developing MI allergy.2 These figures come from people referred for patch testing, not the general population.

What do regulators say?

In 2013 the SCCS concluded that 100 ppm MI was not safe. It found that no safe level for leave-on products, including wet wipes, had been adequately demonstrated.1 The EU banned MI in leave-on cosmetics from 12 February 2017.3 For rinse-off products, the SCCS considered 15 ppm (0.0015%) safe in terms of preventing new allergies.12 The EU adopted that as the limit. Non-compliant rinse-off products could not be placed on the market from 27 January 2018 or sold from 27 April 2018.4 Not every expert body agrees. The US Cosmetic Ingredient Review panel concluded in 2020 that MI is safe in rinse-off products at up to 100 ppm, and in leave-on products when they're formulated to be non-sensitizing.7

Who might want to avoid it?

Anyone with a diagnosed MI allergy. The EU's 15 ppm rinse-off limit is about preventing new allergies. When the SCCS first proposed it, the committee noted that no information was available on whether already-allergic people would react at that level.1 A controlled study shows why rinse-off isn't automatically safe for them. Nineteen MI-allergic volunteers and 19 non-allergic volunteers applied liquid hand soap to their forearms five times a day for up to three weeks. All 10 allergic people using soap with 100 ppm MI reacted, as did 7 of 9 using 50 ppm. None of the non-allergic volunteers reacted.6 No concentration below 50 ppm was tested. Because MI is also used outside cosmetics, people with MI allergy may need to think about other product types too.1

Where does it sit on a label?

On EU-style ingredient lists, look for "Methylisothiazolinone," and for the mixture, "Methylchloroisothiazolinone (and) Methylisothiazolinone" or similar wording.5 Because it's used at very low levels, it typically appears in the final part of the list. EU rules let ingredients below 1% appear in any order after the higher-concentration ones, so its position doesn't reveal the exact amount.5 The SCCS has pointed out that labeling mainly helps people who already know, through patch testing, that they're allergic.1 If you've had an unexplained rash from a shampoo, soap or wipe, a dermatologist can help work out whether MI or something else was the cause.

  1. Opinion on Methylisothiazolinone (P94), Submission II (Sensitisation only), SCCS/1521/13, revision of 27 March 2014. Scientific Committee on Consumer Safety, European Commission, 2013 (revised 2014). https://ec.europa.eu/health/scientific_committees/consumer_safety/docs/sccs_o_145.pdf
  2. Opinion on Methylisothiazolinone (MI) (P94), Submission III (Sensitisation only), SCCS/1557/15. Scientific Committee on Consumer Safety, European Commission, 2015. https://health.ec.europa.eu/publications/methylisothiazolinone-mi-p94-submission-iii-sensitisation-only_en
  3. Commission Regulation (EU) 2016/1198 amending Annex V to Regulation (EC) No 1223/2009 on cosmetic products. European Commission, Official Journal of the EU, 2016. https://eur-lex.europa.eu/eli/reg/2016/1198/oj/eng
  4. Commission Regulation (EU) 2017/1224 amending Annex V to Regulation (EC) No 1223/2009 on cosmetic products. European Commission, Official Journal of the EU, 2017. https://eur-lex.europa.eu/eli/reg/2017/1224/oj/eng
  5. Regulation (EC) No 1223/2009 on cosmetic products, Article 19(1)(g) and Annex V entries 39 and 57 (consolidated text of 18 May 2026). European Union, EUR-Lex, 2009 (consolidated 2026). https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:02009R1223-20260518
  6. Yazar K, et al. Methylisothiazolinone in rinse-off products causes allergic contact dermatitis: a repeated open-application study. British Journal of Dermatology, 2015. https://doi.org/10.1111/bjd.13751
  7. Amended Safety Assessment of Methylisothiazolinone as Used in Cosmetics (Final Amended Report). Cosmetic Ingredient Review, 2020. https://www.cir-safety.org/sites/default/files/MI092020FAR.pdf

Celeiq explains ingredients; it isn't medical advice. If you have a skin condition or reaction, talk to a dermatologist or doctor.