Photoallergic contact dermatitis due to mineral oil

A 39-year-old metal polishing mechanic had had an acute-on-chronic eczematous eruption on sun-exposed skin for 2 years. It improved in winter. He had been using an insoluble oil, CRT 20, as a cutting oil for 20 years. The cutting oil itself and mineral oil, which was one of its ingredients, showed positive reactions on photopatch testing. The difference action spectrum with or without mineral oil application, assessed at 48 h, ranged from 300 to 350 nm, with a peak at 320 nm. This is the 1st report of photoallergic contact dermatitis due to mineral oil.