A large hard scab stuck to the fur on Cassie’s back for over a month. We thought it was from rolling on rigid sharp crusts of ice and snow. A routine visit to the vet revealed the scab was harboring a sebaceous cyst. Several more occurred on her right leg and ear. The vet shaved her fur and exposed a raw, oozing wound.
Sebaceous cysts are common in dogs, but somehow in my many decades of owning dog, I had never seen one. These cysts occur when a pore or hair follicle clogs from dirt, infection, scar tissue or sebum (oil from the skin). I think Cassie got hers from my lack of combing her fur this winter. Her coat is thinning as a side effect from long-term use of prednisone to treat her leukemia. Every time I comb her, she loses more fur and I didn’t want her coat to get too thin during the cold winter.
If the cyst doesn’t break the skin, it often goes away on its own. But if it breaks the skin, bacteria could cause an infection, so keep it clean with daily washing with soap and water. Most of the time the cysts are harmless, unless they become infected. http://www.vetinfo.com/sebaceous-cysts-dogs.html
But don’t squeeze them – watch this video: https://www.youtube.com/watch?v=AsSKDYG6hD0