I have noticed that my Guinea pigs Cheryl and Millie have been scratching an awful lot and biting their legs for the last 2 days, they live indoors and have only newspaper and the dust extraced hay from pets at home in their cage, i dont use wood shavings as Cheryl has a sensitive chest, they dont seem to have any bald patched or anything, i was thinking maybge mites from the hay, but my other piggy Buttercup who lives in a seperate cage and has also had the hay in is not scratching :{