Skip Navigation LinksHome > March/April 2013 - Volume 24 - Issue 2 > Methylchloroisothiazolinone and Methylisothiazolinone Allerg...
doi: 10.1097/DER.0b013e3182811432

Methylchloroisothiazolinone and Methylisothiazolinone Allergic Contact Dermatitis and the Effect of Patch Test Concentration

Higgins, Eleanor MB, BCH, BAO, MSc, MRCPI; Kirby, Brian MB, FRCPI; Rogers, Sarah MD, MSc, FRCPI, FRCP; Collins, Paul MD, FRCPI

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Background: The isothiazolinones methylchloroisothiazolinone and methylisothiazolinone (MCI/MI) are the active ingredients in a frequently used preservative in cosmetic, household, and industrial products.

Objectives: This study reviewed our department’s cases of allergic contact dermatitis caused by MCI/MI, outlining their clinical presentation and possible sources of sensitization. The effect of changing the concentration of MCI/MI from 0.01% to 0.02% in the British Society for Cutaneous Allergy baseline series was also measured.

Methods: A total of 964 patients were patch tested to the British Society for Cutaneous Allergy baseline series in our department over 4 years. Patients were tested either to 0.01% MCI/MI (697) or 0.02% MCI/MI (267).

Results: Twenty-one patients (2.2%) had positive reactions to MCI/MI. Of patients tested to 0.02% MCI/MI, 3.8% had a positive reaction compared with 1.6% of those tested to MCI/MI 0.01%. Ten patients (48%) had perianal dermatitis; of these, 50% had used moist toilet wipes.

Conclusions: We highlight MCI/MI as important contact allergens found in moist toilet wipes and should be considered particularly in patients with facial, hand, and perianal allergic contact dermatitis. Patch testing to 0.01% MCI/MI may underestimate its allergenic potential, missing more than half of allergic cases compared with testing to 0.02%. To identify isothiazolinone allergy, we recommend that 0.02% MCI/MI should be used in baseline series.

© 2013 American Contact Dermatitis Society

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