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Question
i have a three week old guinea pig she has a dime sized bald spot on her head right above her eyes.

Answer
Hello Beth,
Unless it is right on top of her head and is just the way her fur lays then yes. But dime sized sounds way to big to be a head rosette. It might be a skin fungal infection!
I would have the vet take skin samples and see if its contagious!
Hope i helped!
Holly