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A 33-year-old male presented with brown discolouration of the fingernails following the application of 4% hydroquinone in sorbolene cream and 0.1% tretinoin cream to the face intermittently for 9 months.
 adverse event: application 
Please tell me event type and its trigger word from given type options. Output format is "type: trigger".  Option: adverse event, potential therapeutic event 
Text: {0} 
Answer:
 adverse event: application 