Should I worry about dog's bald patch?

A The bald patch near the base of his tail is likely to be tail gland hyperplasia.

- DAVID GRANT

My eight-year-old German shepherd has developed a strange bald patch on his tail. It is oval-shaped and doesn't appear to bother him, but people often point it out when we are out for walks. Have you any idea what this might be?

All dogs have a localised collection of sebaceous glands (the tail gland) in this part of the body. Sebaceous glands produce sebum, which coats hair follicles and is responsible for the glossy appearance of the coat.

They are found in association with all hair follicles but are more numerous in this region of the tail.

The bald patch often develops when there is an excess of the male sex hormone testosterone, causing an over stimulation and swelling of the sebaceous glands, known as hyperplasia, with loss of hair.