I've found this website.. I hope it helps.. Dog Skin Treatment Options | Cysts | Black Skin | Dandruff Dog Skin - Sebaceous Cysts http://www.old-dog-treats-and-rawhid...ceous-cyst.gif
Sebaceous cysts can develop in any dog. Sebaceous glands produce an oily substance (sebum) which helps to keep your dog's skin and coat moist.
This oily substance moves through little ducts from the gland to the hair follicle, then it moves up the hair follicle to the skin. If the hair follicle becomes blocked, the oily substance can't escape. The gland continues to produce sebum which then forms a cyst.
These cysts can become as large as 2 inches in diameter. They're not usually painful, and in many cases they resolve without treatment. If your dog's cyst is not going away, apply a warm compress to see if it loosens the plug blocking the follicle and allows the sebum to drain.
Sometimes the cyst will actually rupture and discharge its contents onto your dog's skin. If your dog spends a lot of time outdoors, the area needs to be kept clean so it doesn't attract flies. Again, the rupture will often heal without treatment. If the cyst doesn't go away on its own, it may need surgical removal.
Your Old Dog: Maintaining Health, Happiness And Nutrition recommends using warm compresses 3-4 times daily on the dog cyst until you see results. Keep in mind that these type of cysts are soft. If you see no improvement or the cyst(s) appear red and bleeding or hard to the touch, make an appointment with your Veterinarian.