Prevalence and cause of methylisothiazolinone contact allergy.

BACKGROUND

Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) has been one of the most frequent sensitizers since the 1980s. In 2005, the use of MI alone was approved for the preservation of cosmetic and household products in the EU. Before that, MI was used in industrial products, and the first cases of isolated MI contact allergy were published.

OBJECTIVES

To present the prevalence and causes of MI contact allergy.

MATERIALS AND METHODS

Patch test results from 2536 dermatitis patients tested with MI at Gentofte University Hospital between May 2006 and February 2010 were analysed. A retrospective investigation of medical records from MI-allergic patients was performed to reveal the causes of their MI contact allergy.

RESULTS

Of patch-tested patients, 1.5% had MI contact allergy. It was associated with occupational dermatitis, hand eczema and age above 40 years. Exposure to MI in cosmetic products was found in 12 (32%) cases, and exposure to MI in occupational products was found in 11 (30%) cases; 5 of the 11 were painters.

CONCLUSIONS

The prevalence of MI contact allergy is already at the same level as that of other sensitizing preservatives, which have been on the market for several years, but no rising trend was identified. MI contact allergy was associated with both occupational and consumer products.