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Ask a Vet: What Causes Sudden Facial Swelling in Cats?

A "cat-fight abscess" is one probable cause; here are facts on symptoms and treatment.

Dr. Eric Barchas  |  Dec 15th 2015


A reader of my website named Jamie recently contacted me about her cat.

I have an outside cat. I left for work one morning and she was fine. I came home for lunch the same day and I noticed that her forehead was swollen. I took her to a vet, but he was not much help. Now it is spreading and getting bigger. Please help.

I get a lot of questions over the Internet, and often my knee-jerk reaction is to think, “Why are you wasting time asking me instead of taking your cat to the vet?” Jamie did, in fact, take her to the vet. Good for you, Jamie. I’m just sorry that it didn’t work out.

Here is what I believe is happening. When an outdoor cat develops a swollen area, it’s an abscess until proven otherwise.

Photo of Dr. Eric Barchas by Liz Acosta

Photo of Dr. Eric Barchas by Liz Acosta

Abscesses occur most frequently when cats develop a locally overwhelming infection. In cats, there are two common types of abscesses. The second-most-common type of abscess is a dental abscess. Such an abscess usually occurs as a result of longstanding dental disease that spreads to the root of a tooth. Swelling occurs in the area, which can cause marked distortion of the jaw or cheek, but not the forehead.

Therefore, I hypothesize that Jamie’s cat has the most common type of feline abscess: the so-called cat-fight abscess.

Outdoor cats are prone to fights with other cats. Many outdoor cats spend much of their time looking for fights. Even those cats who don’t like to fight still may end up tangling with another cat who is itching for an altercation. Abscesses occur when cats are bitten by other cats during fights.

Cats’ teeth, as I’m sure you are aware, are long and sharp

Cats’ mouths, like all mouths, have large populations of bacteria. When a cat bites, bacteria are injected deep into the tissues that are bitten.

Because cat teeth are like needles, the entry wound caused by a cat bite will be small and may heal quickly. At first, a cat bite does not seem like a big deal. But when the entry wound heals, the bacteria introduced by the bite are cut off from oxygen. That’s a good thing for them, but not the individual who has been bitten. A common type of bacteria in cats’ mouths, Pasteurella multocida, thrives in environments where there is no oxygen. A raging infection often occurs.

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An angry cat hisses by Shutterstock

One to three days after the bite, the infection may begin to manifest itself. The area will become swollen, and it often will be painful. Some, but not all, cats may become lethargic and lose their appetites. Some cats may have a fever.

These early (so-called incipient) abscesses can be hard to diagnose. The entry wounds may have healed, leaving no sign of a cat fight. The classic pus pocket that occurs later in the development of an abscess won’t be there. I’m guessing this was the case when Jamie’s cat was evaluated by the vet.

As the abscess progresses, the body sends white blood cells to the area to fight the infection. They become overwhelmed and die. Dead white blood cells in large quantities are what pus is made of. Therefore, as an abscess matures a palpable pocket of fluid — pus — develops.

If left untreated, the skin overlying the central area of the pus pocket usually becomes devitalized due to pressure and poor blood flow. It loses its integrity, and in most cases the abscess eventually ruptures when the pressure of the pus pocket breaks through this section of skin.

Cat-fight abscesses rarely are fatal to cats. Humans who are bitten by cats are at significant risk of death from infection if they do not receive medical attention. However, they are painful and they can weaken outdoor cats, increasing the risk that they will fall victim to predation.

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Cats brace for a fight by Shutterstock

Therefore, cat-fight abscesses should be treated with antibiotics and pain killers. If a pus pocket is present, the abscess should be lanced so that the pus can be drained from the site.

Although there is a high probability Jamie’s cat has a cat-fight abscess, cat owners should be aware that other problems also can cause sudden swelling. Embedded foreign objects (such as foxtails) often cause swelling and may cause abscesses. Penetrating injuries with sharp objects such as thorns may introduce infection in a fashion similar to a cat bite.

Other possible causes of sudden swelling of the face or other body parts include trauma to the area, bleeding into the tissues of the area (a so-called hematoma), and even tumors that have become irritated or infected.

Jamie, your cat needs another trip to the vet. It is likely that by the time another vet examines her the situation will have declared itself sufficiently for a diagnosis to be reached.

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