Lichenoid contact dermatitis secondary to methylisothiazolinone (MI)

Methylisothiazolinone and methylchloroisothiazolinone (MI/MCI) are broad-spectrum preservatives widely used in cosmetics and household and industrial products. It is well known that MI/MCI can cause allergic contact dermatitis with a spongiotic reaction pattern.1 Because of this reaction, restrictions have been placed on the concentration of MI/MCI used in products.2 In recent years the prevalence of allergic contact dermatitis to isothiazolinone preservatives, namely, MI/MCI, has increased dramatically.3 Cosmetic products are some of the major sources of exposure. Lichenoid reactions are rare in allergic contact dermatitis.4 To our knowledge, the occurrence of lichenoid contact dermatitis to MI/MCI has not been reported. We report a case of photo-aggravated lichenoid contact dermatitis in a 63-year-old man secondary to MI.