dandruff in cat

Question
I have two cats - brother and sister - 8/9 yrs old. The boy has
no dandruff and is quite lean, his sister is very fat ( but doesn't
appear to eat much more ) but has horrendous dandruff ( and
always has ). The more I brush her, the worse ir gets! She has
quite thick fur although supposed to be short haired. When I go
to the vet for her flea injections and ask about her dandruff, all
they ask is what am I feeding her on. To me, she gets good
quality food - the sachets of Friskies Go-Cat, Whiskers and
Felix; Purina dried chicken and fish kibble; roast chicken and
occasionally tuna. Any ideas on how to get rid of the unsightly
bits PLEASE?

Answer
Dandruff in cats can be several things.  It can be parasites like mites on the skin, it can be a fungal disease (requires a skin fungal culture), it could be poor absorption or digestion of dietary fats (requires supplemental fats inthe diet), or it could be from allergic skin disease (may require allergy testing or food elimination diet).  

It is difficult for me to be specific with you on the internet without seeing the cat, so I would recommend that you ask your vet about these possibilities.  If you really want to know what is going on with the skin, your vet can do skin biopsies.  These are sent to a pathologist so you will know what type of skin disease is present.