scratching a lot

Question
Hello Kat-I have a 5 year old female short hair guinea pig.
(Jamie) who lives with (oreo) a 8 month old short hair guinea pig. About a week ago by 5 year old started scratching at the sides of her face. (both cheeks) about one inch below her ears and one inch from her mouth.  She scratches so hard that she falls over onto her back like a turtle. today, I also noticed she's shaking her head. We have looked her over and can't seem to find anything wrong. Our other pig seems fine.  We use pine bedding. Same kind for years. The only thing we can think of is that we normaly feed them pellets made from timothy hay.  The last time the store didn't have it so I picked up another brand, it was made with alfalfa and not timothy hay. They have been eatting this for about three weeks.
Could she have an allergy to this food?  Or  

Answer
Hello Joan,

If she doesn't have mites or a fungal infection (skin in those areas look healthy), then she should have her ears and teeth checked out. It sounds like she has irritation in that area causing her to scratch at it. This could be caused by an ear infection or possibly overgrown molars. She should see a vet soon. An ear infection can do permanant damage to her hearing and overgrown teeth can kill her. It's unlikely a food allergy as the symptoms would usually be different. Something is wrong though and she really should see a vet. Good luck!

-kkat
http://www.geocities.com/abyssinianguineapigs