oa Current Allergy & Clinical Immunology - Sensitisation to the preservatives methylchloroisothiazolinone/ methylisothiazolinone and methylisothiazolinone - allergies in the workplace

Volume 32 Number 3
  • ISSN : 1609-3607



Introduction: Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) and methylisothiazolinone (MI) are preservatives commonly used in water-based products to prevent microbial overgrowth. They are used in industrial products such as paints, glues, lacquers and cutting oils as well as in cosmetics and household-cleaning products. Allergic reactions to MCI/MI were reported in the 1980s and this resulted in the review of the concentration of the preservative in products, and its maximum concentration being legislated in Europe in 2016. The concentration of MCI/MI in industrial products and household-cleaning products is not regulated and there are no labelling requirements in terms of product composition. MI was introduced as a preservative on its own and, since its introduction, reactions to this preservative are increasing to the extent that in the United States it was named allergen of the year in 2013.

Methodology: Data from the National Institute for Occupational Health (NIOH) Occupational Dermatology Clinic, South Africa for the period January 2006–January 2018 were analysed to determine the prevalence of sensitisation reactions to MCI/MI and MI. The records of 829 referrals to the NIOH clinic were reviewed retrospectively. MCI/MI and MI-sensitised cases were identified as patients with a positive patch test (1+; 2+ or 3+ reaction) to MCI/MI and/or MI in the European Standard Series (590 tests) and/or the cosmetic (110 tests) series of patch tests.

Results: Of 590 patients tested with MCI/MI, 30 had positive reactions (5.1%; 30/590). When testing MCI/MI as a 0.01% solution from January 2006 to August 2015, 21/445 (4.7%) of those tested were positive, whereas using double the concentration (0.02%) from September 2015 to January 2018, 9/145 (6.2%) were positive. Sensitisation to MI (0.2%) alone, tested since July 2014, was 15/84 (17.9%) of patients tested, with 7/84 (8.3%) reacting to both MI and MCI/MI. Since the introduction of MI, 13.2% (31/234) of patients tested with these preservatives were sensitised to either MCI/MI and/or MI.

Conclusion: Sensitisation to MCI/MI and MI was shown to increase over the years. Although patch testing with more sensitive reagents may contribute to this, the number of patients sensitised to the two preservatives, both occupational and non-occupational, has increased, and this is in line with international studies. Since these are commonly used preservatives, their concentration in industrial and self-care products needs to be reduced and properly labelled. The concentration for testing is also important to prevent false-positive or -negative reactions.

Loading full text...

Full text loading...


Article metrics loading...


This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error