An abscess is a localized pocket of pus contained in a walled-off cavity, usually just under a dog’s skin (although they can develop internally). Abscesses frequently are associated with scratches, bites, puncture wounds or other skin surface abrasions. Bacteria enter the site of the wound, multiply and start digesting the healthy surrounding tissue, causing inflammation and an infection. The byproduct of this process is the thick, yellowish substance commonly called “pus.” As they enlarge and harden, abscesses put pressure on nearby tissues and nerves and can be extremely painful, especially when they rupture. The infection can spread through the blood to other parts of a dog’s body, leading to systemic illness. This can cause a potentially life-threatening condition called “sepsis.” Owners should familiarize themselves with the causes and signs of abscesses, so that they can get treatment for their affected dogs as quickly as possible.