The skin of all mammals (including cats, dogs and people) grows from a base of replicating cells. The top layer of skin, called the epidermis, continuously flakes off and is replaced by new material from the base of replicating cells.
Most of the time the flakes are small and are not produced excessively. However, some individuals prolifically produce large flakes of skin–dandruff. In extreme cases, animals’ hair may be completely covered in flakes. This syndrome is called seborrhea.
Dandruff is most noticeable in dark-haired individuals. However, it can occur in any mammal.
Certain diseases and syndromes, such as thyroid problems and diabetes, predispose animals to dandruff. However, most cases of dandruff are not related to a major systemic disease process.
If you haven’t already done so, talk to your vet about your cat’s dandruff. He or she should be able to determine whether a medical problem is contributing to the flaky skin. For the record, I have not noticed a correlation between feline asthma and dandruff. I have observed that overweight cats appear to develop dandruff more often than their svelte counterparts.
Some pets with dandruff will respond to special shampoos available through veterinarians. However, if your cat’s skin isn’t itchy or irritated you should not feel obliged to do anything about her dandruff. In most cases, dandruff is strictly a cosmetic problem. And, since cats generally do not derive much of their self esteem from their physical appearance, the situation is probably harmless.
Note about image: do not use human dandruff shampoos on pets.