Why does my cat have dandruff?

A small amount of dandruff on a cat is normal, because normal skin-cell turnover also produces some flakes; in dry weather there is a bit more, and the owner need not worry. But if the cat has a lot of dandruff and sheds heavily, it may be from bathing too often or using harsh products — never use human body wash on a cat, and keep baths to about once every 2 to 3 months.

Finally, if the cat has heavy local scaling with broken or lost hair, it is very likely infected with ringworm, and you should treat it promptly to stop the fungus spreading.