They probably can- thier sense of smell makes a dog look snoutless, and IIRC they see into the UV spectrum so they might be able to actually see if something has been applied recently.

I'm just glad I don't see in the UV spectum. *shudders*
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-IronRaven

When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.