The patterns of hair growth vary with species and anatomic location on the body. For some cats, seasonal alterations are noted. In dogs and cats, a mosaic exists and coordinated shedding cycles occur.
In some breeds the active or growing part of the hair cycle is prolonged, as in Yorkshire terriers, like it is in people. These breeds are more sensitive to drug therapy, like chemotherapy, that interfere with the hair cycle, and they develop alopecia as an adverse effect. These affects are less common in cats.
Numerous factors affect hair growth in cats. They include:
If your cat has been clipped and the hair is failing to grow back, it may be due to a hormonal deficiency or imbalance. In order to diagnose this, blood samples are necessary to measure concentrations of various hormones.
If your cat is losing hair in spots then it may have a bacterial infection or ringworm or demodicosis. Your veterinarian may need to do skin scrapings or pluck hairs for cultures.
Prevention and follow-up depends on the cause for the lack of hair growth. As a general rule, the use of steroids should be limited or avoided as they cause medical problems and arrest hair growth.