An update of the risk assessment for methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) with focus on rinse-off products

Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) has been widely used during the last 20 years for the preservation of aqueous systems in cosmetics, toiletries and in various industrial applications. MCI/MI has a broad spectrum of activity against fungi and bacteria at very low concentrations. The allergic contact potential of MCI/MI has been known for many years. This paper provides a review of pre-clinical and clinical experimental studies as well as experience from dermatology clinics worldwide. This forms the basis for an update of the risk assessment for the use of MCI/MI in rinse-off products. The scientific data indicate that the actual sensitization rate observed with a contact allergen is extremely dependent on dose and type of exposure. This review of the data leads to the conclusion that, under normal use conditions, within the current permitted/recommended use concentrations for MCI/MI of up to 15ppm, the risk of primary sensitization from the use of rinse-off products is negligible, and elicitation of allergic contact dermatitis in MCI/MI-sensitized individuals rare, after exposure to MCI/MI-preserved rinse-off products.     

“Slime” contact dermatitis: Case report and review of relevant allergens

Homemade “slime” is currently a popular childhood hobby that can cause allergic and irritant contact dermatitis. We describe a case of hand dermatitis due to homemade “slime” with a positive patch test to methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) and MI. The most common potential allergens in “slime” collected from a review of “slime” recipes found on the Internet are reviewed.     

Occupational dermatoses in a plant producing binders for paints and glues

A survey of occupational dermatoses, based on a questionnaire, clinical examination and patch testing, was carried out among present and former employees in a plant producing binders for glues and paints. The binders are chemically based on vinyl acetate and/or acrylates. Preservatives are needed and those based on methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) are the most commonly used. The questionnaire was answered by 83 out of 85 present employees (97.6%) and 12 out of 15 former employees (80.0%). 76 of the present (89.4%) and 11 of the former employees (73.3%), respectively, participated in the clinical examination and patch testing, which was conducted with a standard test series and chemicals from the work environment. Occupational dermatosis was diagnosed in 22 present workers (28.9%). Irritant and allergic contact dermatitis was demonstrated in 9 (11.8%) and 13 (17.1%) employees, respectively. Occupational contact allergy to acrylates and formaldehyde was detected in 3 workers and 1 worker, respectively. 12 individuals (9 present and 3 former production workers) had an occupational contact allergy to MCI/MI. 4 of the present workers had spilled Kathon LX on their skin resulting in chemical burns and allergic contact dermatitis. In total, the figure for occupational skin diseases among all present production workers was 40.4%.