Methylchloroisothiazolinone and/or methylisothiazolinone in cosmetic products—A market survey

Background: There was a global epidemic of methylchloroisothiazolinone (MCI) and/or methylisothiazolinone (MI) contact allergy from 2009 to 2015. In response, the Thai Ministry of Public Health regulated the use of MCI/MI in cosmetics. Objective: To survey the presence of MCI/MI and MI alone, as labelled on cosmetics sold on the Thai market, before and after the ministerial directive. Methods: The presence of MCI and/or MI in leave-on and rinse-off cosmetics sold on the market, based on the labelling of ingredients in 3445 products, was analysed. Results: Before the implementation date, most leave-on products contained MCI/MI. After the regulations came into force, the only leave-on cosmetic subcategories that complied with the law were facial skin-care, sunscreen and make-up products. MCI/MI and MI alone were found on the labels of both leave-on and rinse-off products, the presence of each varying between product subcategories. Conclusions: Despite the ministerial regulations restricting their use, MCI and/or MI are still found in cosmetics sold on the Thai market. Dermatologists should be aware of this situation, and counsel patients to avoid products containing MCI and/or MI.