Methylchloroisothiazolinone and methylisothiazolinone contact allergy: an occupational perspective

Sensitivity to either methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) or MI has increased, with a reported frequency of up to 11.1% among dermatitis patients, the main context being allergic contact dermatitis caused by MCI or MCI/MI in personal care products. Case reports have described occupational allergic contact dermatitis caused by MI in paints and within the beauty industry.

This study identified incident cases of occupational allergic contact dermatitis caused by MCI/MI and or MI reported from 1996 to 2012 to a UK-wide surveillance scheme (EPIDERM), with the aim of identifying changes in incidence over the study period.

The data show an increase in occupational allergic contact dermatitis caused by MCI/MI and or MI from 1996 to 2012 of 4.1% [95% confidence interval (CI) 1.6-6.9] per annum. Analysis by industry showed a 3.8% (95% CI: -0.3 to 8.0) per annum increase in those exposed to personal care products in the workplace as a primary exposure [healthcare workers, 8.1% (95% CI: 2.1-14.4) per annum; beauty workers, 6.6% (95% CI: -2.2 to 16.2) per annum; hairdressers, 1.5% (95% CI: -4.7 to 8.1) per annum]. There was a 6.3% (95% CI: 1.8-10.9) per annum increase for manufacturing workers. A statistically significant rise in the frequency of occupational allergic contact dermatitis was shown to be attributable to MCI/MI and or MI between 1996 and 2012.

The findings support recommendations for a review of the regulations relating to MCI/MI and/or MI in cosmetic and personal care products and in industrial settings.