An abscess is a pocket of pus that develops when a wound of some sort becomes infected. Abscesses can occur almost anywhere within a dog's body, including the brain, liver, and lungs, but more often, abscesses are fairly superficial, and develop in the animal's anal glands, at the root of a tooth, or just below the surface of the skin. Left untreated, an abscess can become chronic, or even cause a life-threatening infection that affects the functioning of your dog's internal organs, so it's important to always seek veterinary attention should your dog develop an abscess.

What Is an Abscess?

An abscess results from the body's attempt to wall off an infection. The fight against infection results in an accumulation of white blood cells and other blood components commonly called pus. This thick liquid collects in a fleshy pocket in the affected body area, which then swells and becomes very painful. This swollen pocket of infection is called an abscess.

Almost anything, such as a bite wound, splinter, or even an insect sting, can result in an abscess if the surface of the skin is penetrated and bacteria are introduced. If the skin surface heals over the wound superficially, the bacteria can become sealed inside, triggering activation of the body’s immune system and the development of an abscess.

Some abscesses can also occur internally from bacteria or foreign material that gets in through the digestive tract, urinary tract, respiratory tract, or other ports of entry into the body.

Symptoms of Abscesses in Dogs

The symptoms of an abscess can depend on where it is located. For those in the skin, a soft or firm lump is the most common indication of trouble brewing. The area around the lump will often be red, and the dog may lick or bite at the spot in an effort to relieve the pain. The inflamed skin usually will feel warmer than the surrounding skin, as well.

Pus

If your dog's skin abscess is hidden by thick fur, it's possible you won't even realize it is there unless it bursts, releasing pus and fluid that typically has a strong, foul odor. But you might discover the abscess prior to that if you notice your dog biting or licking at the sore spot or you feel the lump while petting your dog. If the abscess is present for a long time, hair loss over the spot is not uncommon.

Lethargy

Your dog might seem more lethargic than usual, or reluctant to participate in activities it usually enjoys, such as walks. Fever might also develop, particularly with a large or widespread abscess.

Scooting

When dogs develop abscesses in their anal glands, they often scoot their rear ends along the ground in an attempt to relieve the pain. The dog might also lick or bite at the area, and there may be fluid or pus coming from the wound.

Refusal to Eat

Dogs with abscessed teeth typically become reluctant to eat, due to the pain. Your dog might especially refuse kibble, as the hard food is more painful to chew than soft, canned meals. Often, the dog's face will appear swollen under the eye, as the roots of the teeth extend into this area.

What Causes Abscesses in Dogs?

Abscesses are usually caused by a bacterial infection taking hold within some type of wound. If the surface of the wound heals quickly, bacteria can become trapped beneath the skin, creating a pocket of infection. Some of the species of bacteria that are especially likely to be the culprit include Staphylococcus, Pseudomonas, Mycoplasma, Escherichia coli, Bartonella, Nocardia, Pasteurella multocida, and Actinomyces. But while bacterial infection is the underlying cause of the abscess, there also needs to be some type of event that allows the bacteria access inside the body.

Bite Wounds

Bite wounds from another animal that plant infectious organisms deep into the tissue are a prime cause of abscesses in dogs. This is especially common in dogs that tend to fight with other dogs, or dogs who tangle with cats and get scratched or bitten. But any animal bite can potentially become infected and abscessed.

Penetrating Wounds

Any injury that penetrates the skin can lead to an abscess. A poke from a stick, an accidental needle prick, stepping on a thorn, or an insect bite are all potential causes of this type of infection.

Dental Issues

Abscesses may result from chewing an inappropriate object that splinters and injures the mouth, such as a bone, stick, or piece of plastic. In these cases, the abscess may develop on the tongue, gums, cheek, or behind the eye. A dog can also get an abscess in the root of a tooth that breaks or cracks due to chewing a hard object.

Anal Glands

Dogs also commonly suffer from anal gland abscesses, in which the area around the rectum becomes red, swollen, and tender. If the abscess bursts, you may notice smelly, wet hair at the infection site.

How Do Vets Diagnose Abscesses in Dogs?

Your veterinarian will probably make the diagnosis of an abscess from the characteristic appearance and symptoms. Occasionally, your vet might want to use a needle to withdraw a sample of fluid from the abscess, or swab draining fluids, to perform a culture and sensitivity, which is a laboratory test that determines the type of bacteria present, along with the specific antibiotics that kill that bacteria.

How to Treat Abscesses

Because it is crucial that an abscess be completely drained, but doing so is very painful, your vet will probably sedate or anesthetize your dog before beginning to work on the wound. First, the hair around the swelling is clipped and the area is disinfected with a surgical scrub solution like povidone iodine. Then the abscess is lanced, the pus is drained, and the abscess is flushed with a saline solution to clean out the inside of the infected pocket.

When the abscess is very deep or intrusive, a drain or “wick” may be surgically stitched in place to keep the area draining as the surface skin heals. This can help prevent the abscess from recurring. Oral antibiotics are usually prescribed as well. When the surgical site is within reach of your dog's teeth, an Elizabethan collar or e-collar prevents your dog from bothering the wound while it heals.

Don't try to lance or squeeze an abscess yourself. You are unlikely to fully drain the wound, and there is a chance your dog will bite you due to the pain. However, after treatment by your veterinarian, you may be given instructions on cleaning the wound site at home while it heals. This generally involves gently wiping the area daily with a wet cloth to remove draining fluids.

Prognosis for Dogs with Abscesses

Once your dog's abscess is drained fully and a course of antibiotics is completed, the wound should heal fully without further trouble. If the abscess isn't treated, however, or is only partially drained, the wound will persist and can spread into the dog's bloodstream or to nearby organs.

How to Prevent Abscesses

Help prevent abscesses by reducing the probability of injury. For example, neuter or spay your dog to greatly diminish aggression that could result in bite wounds. Also, supervise your pet when it's gnawing on dog chews or bones, and only offer safe options. Good dental hygiene and routine care of anal glands will help reduce the risk of abscesses in these areas as well.