Background: Photoaggravated allergic contact dermatitis caused by methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) and MI has been reported.
Objectives: To describe the clinical characteristics and results of (photo)patch tests and photo-tests of 10 patients in Belgium and France suffering from photoaggravated contact dermatitis caused by MI.
Patients and methods: Five men and five women, with a median age of 49.5 years, were investigated between January 2012 and February 2017 because of suspected photoaggravated contact dermatitis. Patch tests, photopatch tests and/or photo-tests were performed.
Results: Seven patients had positive patch test reactions to both MCI/MI and MI, whereas 3 patients had positive patch test reactions only to MI. In most cases, MI was the (strong) primary sensitizer. Photopatch tests with MCI/MI and/or MI gave stronger reactions than patch tests with these derivatives, indicating photoaggravation. Sensitization probably took place from cosmetics and work-related biocides, whereas elicitation of dermatitis was remarkably often related to airborne exposure to MI present in paints or industrial biocides. Four patients suffered from transient photosensitivity.
Conclusion: Photoaggravated allergic contact dermatitis and transient photosensitivity caused by MI is a peculiar clinical presentation of allergic contact dermatitis caused by this preservative, and should be considered in daily clinical practice.
Keywords: airborne allergic contact dermatitis; cosmetics; dilution series; methylchloroisothiazolinone; methylisothiazolinone; occupational; paints; photo-tests; photoaggravation; photosensitivity; sunscreens.
© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.