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Perioral leukoderma simulating vitiligo developed in a 25-year-old woman. A patch test to cinnamic aldehyde was positive; depigmentation was observed at the patch test site three months after initial application. No changes in pigmentation occurred from a concomitant allergic patch test reaction to neomycin sulfate; only hyperpigmentation occurred at the site of an irritant patch test reaction to nonanoic acid. A toothpaste containing cinnamic aldehyde was implicated; perioral hypopigmentation resolved when a toothpaste without cinnamic aldehyde was substituted. A repeated patch test to cinnamic aldehyde again showed depigmentation at the patch test site three months after application.
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C. G. Toby Mathias (1980) studied this question.
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