One of my guinea pig has two big bald patches. She is not scratching, the bald spots are not red, they aren't chapped or anything. it almost looks like she was shaved. it is smooth and light pink.
She is eating and drinking fine and her bowels are fine. she is not lethargic and her eyes are wide and bright.
She doesn't appear to be sick or to have anything wrong with her skin.
What could cause this?