Abscesses

An abscess is a pocket of pus that forms under the skin or inside the body when bacteria get in and the immune system walls off the infection rather than letting it spread freely. The pus itself is a mix of dead white blood cells, bacteria, and damaged tissue, and it builds pressure inside a capsule the body forms around it. Most abscesses in pets start with something quite ordinary: a bite wound, a scratch, a puncture from a stick or thorn, or a gland that has become blocked, which then gets colonised by bacteria such as Staphylococcus, Streptococcus, or Trueperella species.

Cats are especially prone to abscesses after fights, because their sharp teeth leave small puncture wounds that seal over quickly and trap bacteria underneath, exactly the environment an abscess needs to develop. Dogs commonly get them around the anal glands when the sacs don't empty properly and the trapped material becomes infected, or in the neck and mouth after a stick injury works its way under the skin. Wherever it happens, an abscess usually looks like a swollen, warm, painful lump, and the animal is often reluctant to have it touched. If it has burst, you may notice a foul smell, matted fur, or a draining wound. Depending on location and cause, an affected pet can also run a fever, go off food, or seem generally low, since the infection is putting strain on the whole body.

Watch for:

• A swelling that comes on quickly: especially if it's warm, tender, or gets bigger over a day or two
• Sudden lameness or reluctance to bear weight: which can point to an abscess in a paw or joint
• Scooting or licking around the tail base: a common sign of an anal gland problem in dogs
• Discharge, a bad smell, or a wound that won't heal: suggesting the abscess has already ruptured
• Fever, lethargy, or loss of appetite: signs the infection may be affecting the animal more broadly

Left alone, a small abscess can sometimes rupture and drain on its own, but many need a vet to lance and flush them properly, and a course of antibiotics is often part of treatment. Larger or deeper abscesses, such as those inside the abdomen or around the eye socket, are diagnosed with imaging or fluid sampling and can need more involved treatment, sometimes surgery, sometimes prolonged antibiotics guided by culture results. The real risk with abscesses isn't usually the pocket of pus itself, it's what happens if the infection isn't dealt with: it can track along tissue planes, damage nearby structures, or get into the bloodstream and cause a body-wide infection, which is a genuine emergency. That's why any lump that's growing, painful, or draining is worth a same-day or next-day vet visit rather than a wait-and-see approach. The guides below go into specific types of abscess in more depth, including where they tend to occur and what treatment usually looks like.