Methylisothiazolinone (MI) is a biocide which is effective in low concentrations. Biocides are needed to prevent growth of microorganisms in products containing water, such as most cosmetics, skin care products, soaps, paints, cutting oils etc. MI has for decades been used in combination with methylchloroisothiazolinone (MCI) as a biocide in a 1:3 combination. Around 2000, MI was introduced as a standalone biocide first in occupational products and from 2005 permitted in cosmetics in 100 ppm (0.01%), which is a 25-fold higher concentration than in the MI/MCI combination. The first occupational cases of MI allergy, which were due to paints, were published in 2004 and from cosmetic products, which were due to wet wipes, in 2010. Thereafter, the continued use of MI as a biocide in cosmetic, household and industrial chemical products has resulted in an unprecedented increase in the incidence of contact allergy to MI in Europe, US and Australia.



Scientists, national health and environmental authorities have for several years tried to raise awareness of the European outbreak of contact allergy to MI. In 2013, the European Commission (EC) requested an opinion (SCCS/1521/13) from the Scientific Committee of Consumer Safety (SCCS). The SCCS concluded that ‘For leave-on cosmetic products 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.’ After the submission of additional data from cosmetic industry concerning the safety of MI in rinse-off cosmetic products and stay-on hair products, the SCCS published a new opinion (SCCS/1557/15) and arrived at the same conclusion as in their earlier opinion (SCCS/152/13). Based on this EU member states agreed on a ban of MI in leave-on cosmetic products, which has been in effect from early 2017. In March 2017 the member states agreed on limiting the use of MI in rinse-of cosmetic products to 15 ppm, as suggested in the SCCS opinion; the implementation date is not known. Concerning industrial products it was agreed by member states in spring 2017 that MI is a contact allergen and the warnings (H317) should be in the safety data sheet and/or on the product label if MI is present in or aboveat ≥ 15 ppm in industrial products and MI mentioned as an ingredient (labelling) if present at ≥ 1.5 ppm.[i]


European Study on MI Contact Allergy

Even though a lot of data on MI contact allergy epidemiology in individual countries had been published, no pan European studies had yet been launched concerning crucial exposures to MI. The European Environmental Contact Dermatitis Research Group (EECDRG) obtained an EADV grant 2015 to perform such a prospective study across many European countries in order to  provide more detailed data to support the regulation process, and to monitor  potential intervention effects.

A study was launched in 11 dermatology departments from 8 European countries (Belgium, Denmark, Finland, United Kingdom, Italy, Portugal, Spain and Sweden) and data prospectively collected for 6 months in 2015 using a standard case record form among consecutive patients who were patch tested positive to MI. In this baseline study data from 3434 patch tested patients were collected, of whom 6.0% were allergic to MI, with a broad range from 2.6% in Bari, Italy, to 13% in Helsinki, Finland. The majority of these were incident cases as they had noted onset of their dermatitis between 2013 and 2015. The MI allergic patients most often had hand and/or facial dermatitis. In 2 out of 3 patients MI was found of current relevance, which means that a current exposure could be identified which had caused or significantly contributed to the dermatitis, mostly exposure to MI in both rinse-of and stay-on products cosmetic products. In 16.8% of patients relevant occupational exposures were identified such as cleaning agents, water-based paint, glue, lacquer, and/or cosmetic products and household products at the work-place. In total 7.3% of patients with MI contact allergy had experienced allergic reactions due to airborne MI exposure when staying in newly painted rooms.[ii]


The EECDRG continued collecting data on MI allergic patients in 2016 and currently for 2017 in the EADV-supported project. The data will reveal if there are any first effects of the regulatory steps taken. Publication is expected in 2018. Together with surveillance data on morbidity, exposure information thus collected will enable evaluation of the success of interventions thus far achieved, and may identify further areas where action is needed.



Clinically relevant MI contact allergy remains prevalent across European countries mainly due to exposure to cosmetic products, with a shift from leave-on to rinse-off type products.


[i] (Editorial) Methylisothiazolinone – quo vadis? Contact Dermatitis 2016; 75: 263-4

[ii] Schwensen JF, Uter W, Bruze M, Svedman C, Goossens A, Wilkinson M, Giménez Arnau A, Gonçalo M, Andersen KE, Paulsen E, Agner T, Foti C, Aalto-Korte K, McFadden J, White I, Johansen JD; European Environmental Contact Dermatitis Research Group. Contact Dermatitis 2017; 76: 272-9


Authors: Profs. Jeanne Duus Johansen and Wolfgang Uter