My 16 yr old short hair domestic cat is having a serious problem with undercoat hair.  I brush her and bath her and still she comes out looking like I had done nothing to remove the undercoat.  I feed my cats the best of the food so I don't think it is diet, she has only started this approx 6 months ago.   Please let me know what I can do to remove this undercoat once and for all.  Thank you.