Ruptured Cyst On Dog. Sebaceous cysts are prone to rupture and consequential episodes of bleeding. Trimming will also prevent the discharge from crusting on the fur.
If necessary, trim the area around the cyst to gain access and allow for direct contact with the cyst. You can use soapy water and wash it well, then use hydrogen peroxide, and neosporin to keep the bacteria under control. Small, uncomplicated cysts are typically left alone.