Have got a Lurcher with the same problem could be the Sebaceous glands
Stud Tail
(Supracaudal Gland Infection)
There is a sebaceous gland near the base of the tail in both dogs and cats that sometimes becomes over-active and/or infected. In cats, this condition is called "stud tail" even though the problem sometimes occurs in females and castrated males.
In dogs, the same condition is usually just called by it's medical name: Supracaudal Gland Infection or Supracaudal Gland Hyperplasia.
If no underlying problems (typically fleas) are found, then treatment consists