A 33-year-old woman presented to our clinic for suspected photoallergic contact dermatitis with a recent episode of severe, vesicular dermatitis involving exposed skin and correlating with relocation to a new home. Biopsy results showed spongiotic and lichenoid dermatitis with eosinophils. Patch test results showed a very strong (+++) reaction to methylisothiazolinone (MI), mild (+) reaction to MI/methylchloroisothiazolinone, and no reaction to benzisothiazolinone. These allergens were found in several personal products. However, the patient was suspicious of 4 wall paints recently used in her home. Semiopen patch tests to 3 Behr interior paints showed positive results. Nine controls showed negative results. High-performance liquid chromatography demonstrated MI and benzisothiazolinone in all 4 paints at concentrations ranging from 50 to 100 ppm and 290 to 340 ppm, respectively. Although MI has been reported to cause occupational airborne contact dermatitis in European household painters, to our knowledge, this is the first documented case of paint-related MI allergy in the United States.