Abscesses in Dogs and Cats — When Wounds Fill With Pus

By the time an abscess is obvious, antibiotics are required to fight the infection and keep the cat healthy.

Some abscesses may require minor surgery. By: Pat Cullen
Some abscesses may require minor surgery. By: Pat Cullen

An abscess is a localized buildup of pus that occurs in a dog or cat when bacteria penetrate tissue — usually as a result of a fight or minor injury.

Be warned: The pus inside an abscess can be stinky stuff. (That said, I once worked with a vet tech who so loved cleaning up abscesses that she counted it as a perk of the job.)

Symptoms of an Abscess

A typical example is a cat bite abscess. Your cat gets into a scrap, and a couple of days later he is quieter than usual and gone off his food. You find a swelling on his flank, but when you try to look closer, a normally placid cat hisses and growls. Does that sound familiar?

After the initial injury, it can take 2 to 5 days for the abscess to develop.

In the early days, you might stroke your pet and find a clump of sticky hairs, or a scab, marking the site of a small wound. This area may be tender and warm to the touch. As infection brews beneath the surface, pus builds up and a swelling develops.

If an abscess bursts, don’t panic. Pus can be foul-smelling and bloodstained, which looks dramatic, but the animal is in no danger of hemorrhage.

The size of an abscess can range from a blister between the toes (caused by a grass awn) to extremely large. Last year I treated a Golden Retriever with an abscess the size of a football.

What Causes Abscesses in Dogs and Cats?

Any injury that penetrates the skin’s protective barrier can result in an abscess.

That said, anything that pierces the skin, such as a grass awn between the toes, can set off an abscess. The body is a wonderful thing and tries to “wall off” the infection, hence the formation of a lump filled with pus.


Your vet will be suspicious of a skin abscess from the animal’s symptoms and history, such as a recent fight, going off food and running a fever.

Confirming the diagnosis is easily done (provided the patient is not too sore) by popping a needle into the swelling and seeing if pus drips out. Dental abscesses can be tricky to diagnose, and dental radiographs are necessary to identify exactly which tooth is causing the problem.

Treatment of an Abscess

By the time an abscess is obvious, a course of antibiotics is required to settle the infection. Most vets use a broad-spectrum antibiotic that is effective against the staphylococci bugs found on the skins surface.

Rarely, the abscess fails to respond, in which case a sample of pus is cultured to find out exactly which bacteria are present, and which antibiotic will kill them.

This video shows veterinarian Dr. Meredith Kennedy explaining abscesses and treatment on Rocky, a female Labrador:

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An important part of treatment is to:

  1. Lance the abscess.
  2. Drain the pus out.
  3. Flush the cavity.

This is a minor surgical procedure and is often done with the patient sedated because it can be sore and uncomfortable.

How to Prevent an Abscess

If you find a fresh wound on your pet, bathing the injury with a weak disinfectant can reduce the contamination and the risk of abscess formation.

I’m a big fan of salt water:

  1. Mix 1 teaspoon of salt into 1 pint of freshly boiled water and leave it to cool.
  2. Simply soak some cotton wool or lint in the disinfectant and use it to thoroughly clean the area.
  3. Please note: Phenol-based disinfectants are toxic to cats. If in doubt about their suitability, check with your veterinarian before use.

Another important prevention is getting your animals neutered. Intact animals are more likely to roam and get into fights over territory.

Finally, the location of an abscess can tell a lot about a cat’s character. An abscess on the head means he was standing up to the opposition, whereas an abscess on the rear means he was running away.


  • Small Animal Internal Medicine. Nelson & Couto. Publ: Mosby. 3rd edition.


This pet health content was written by a veterinarian.