When to see a vet urgently
Contact a vet promptly if a wound or swelling is accompanied by any of the following:
- Your cat is very subdued and does not eat or drink normally.
- The swelling is very painful or your cat cannot bear weight on a leg.
- The wound bleeds heavily or has visible deep damage.
- Redness, pus or swelling increases during treatment and general condition worsens.
Even a bite that looks small needs veterinary assessment. You can find a vet near you.
Overview
An abscess is a defensive reaction intended to contain infection. When bacteria enter tissue, inflammation develops and a capsule forms, inside which pus accumulates. Externally, an abscess looks like a painful swelling or lump under the skin. It may later burst on its own, releasing pus and an unpleasant smell.
A small bite hole can close quickly at the surface even while bacteria carried in by a tooth remain deeper in the tissue. Hair conceals the mark, and you may not notice the injury straight away. Closed skin in this situation does not mean the wound has healed.
An abscess may feel firm initially and later become a softer, fluid-filled swelling. Inflammation can also spread through tissue beneath the skin without a clearly defined cavity of pus. This more extensive tissue inflammation is called cellulitis. It cannot be drained in the same way as an abscess that has formed a cavity.
Causes
The main causes of bacterial abscesses in cats include:
- bites from other animals, particularly during fights
- scratches and skin injuries
- bacteria entering tissues, such as Staphylococcus, Streptococcus and Pasteurella multocida
- infection caused by foreign objects, such as splinters
Several bacterial species can be present in the same abscess, so appearance alone does not identify the pathogen. Some bacteria in deep abscesses grow in low-oxygen conditions. If a foreign object remains in the tissue, the abscess can recur even if discharge is removed for a time.
An abscess under the skin is distinguished from other types. For example, a tooth root infection can cause facial swelling, and an abscess beside the anus may involve an anal gland. Treatment in these cases also targets the original diseased structure. The bite abscess care described here therefore does not apply unchanged to every swelling.
Risk factors
- Unneutered male cats that fight over territory.
- Cats with outdoor access.
- Cats with weakened immune defences.
- Untreated wounds after injuries.
A disease or medication that weakens immune defences can make infection harder to control. FIV infection, for example, damages the immune system. However, a single abscess does not show that a cat has a viral infection. Infection risk is also considered after fighting injuries: FIV spreads primarily through bites from an infected cat.
Symptoms
Typical signs include:
- a painful swelling in the skin
- local redness and swelling
- fever
- lethargy and reduced activity
- loss of appetite
- pus and a bad smell when the abscess bursts
- sometimes lameness if the abscess is on a paw
A change in behaviour may precede a visible lump. A quieter-than-usual cat may withdraw, avoid touch or repeatedly lick one area. Pain can also appear as growling or unusually defensive behaviour. A bite at the tail base can cause a cat to hold its tail limply, while a limb injury causes lameness.
Common bite sites include the head, neck, front legs and tail base. You can look gently if your cat allows it, but do not squeeze a painful lump or force your cat to be examined. If a fight is known to have occurred, contact a vet before waiting for a visible abscess to form.
Possible complications
An untreated abscess can lead to:
- infection spreading into surrounding tissues
- draining tracts and chronic sites of inflammation
- sepsis, with infection spreading throughout the body
- marked weakening of the body due to ongoing inflammation
An abscess bursting may briefly relieve pressure and pain, but does not guarantee that the infection has resolved. Pus or damaged tissue may remain in the cavity. If the opening closes too early, inflammation can continue beneath the skin and discharge again.
A fistula here means a tract in the tissue through which a deeper infected site drains onto the skin surface. Persistent discharge or repeated swelling at the same site is a reason for further investigation. Foreign material or an unusual bacterium may be responsible, for example, and cleaning the surface alone does not resolve the problem.
Diagnosis at the vet
Diagnosis is usually based on clinical examination. Where necessary, your vet may carry out:
- needle sampling of the abscess and examination of its contents
- blood tests to assess general condition
- bacterial culture to identify the pathogen
At the appointment, your vet establishes when symptoms began, whether a fight may have occurred and what treatment has already been given. The whole cat is examined because the size of a visible bite hole does not reveal the extent of tissue damage. Your vet also assesses pain, hydration and general wellbeing. An unwell cat may need more extensive supportive care than an otherwise well cat with a localised abscess.
A lump is not always an abscess. A cyst, haematoma or tumour, for example, can look similar from the outside. A fine-needle sample taken by your vet provides information about its contents; a biopsy may be needed if the cause remains unclear. You can record the lump's size and appearance and photograph it before the appointment if this can be done without hurting your cat. Growth, changes in shape, discharge and tenderness provide useful background information. Do not label a new lump an abscess simply because your cat has had one before.
Bacterial culture and susceptibility testing are particularly important in persistent or recurrent infections or those responding poorly to treatment. Results allow medication to target the bacterium found. If healing differs from what is expected, your vet may also assess the need for FIV and FeLV testing. A recent FIV exposure may not immediately show on an antibody test, so repeat testing is agreed according to the situation.
Treatment
Removing pus and cleaning the cavity are central to treatment. Handling the area may require sedation or general anaesthesia so painful tissue can be examined safely. Dead tissue is removed and a foreign object sought where necessary. Do not open an abscess yourself at home.
The wound may be left open to allow discharge to escape. Sometimes a drain is placed to prevent fluid accumulating beneath closing skin. An open wound therefore does not mean treatment is unfinished. Wound closure, any dressing and the timing of follow-up are determined by the findings.
Pain relief is part of treatment. The need for an antibiotic is assessed individually according to the extent of infection, general condition and investigations; not every properly drained localised abscess needs the same medication. If an antibiotic is prescribed, give it as instructed. Do not change medication or use another animal's leftover medicines on your own initiative.
Home care and monitoring healing
Ask for written instructions on cleaning the wound and caring for any drain. Use only cleansers recommended by your vet. Alcohol, hydrogen peroxide and many household disinfectants can damage tissue or slow healing. Do not apply essential oils or your own creams to the wound without instructions either.
Prevent wound licking, for example with a suitable protective collar. Saliva does not disinfect a wound and can introduce more bacteria. Keep your cat indoors during recovery and restrict vigorous activity as instructed by the clinic. Handling a drain or dressing is demonstrated at the appointment where necessary; do not remove a drain yourself.
Monitor eating, drinking, activity, swelling, and the amount and appearance of discharge. Contact the clinic if your cat does not become brighter, discharge increases or pain worsens. Some superficial abscesses heal quickly after drainage, but deep tissue damage, a foreign object or a disease weakening immunity can prolong recovery. An agreed follow-up helps assess whether treatment needs changing.
Prevention
- Limit contact with outdoor cats and prevent fights.
- Treat all wounds and scratches promptly.
- Keep vaccinations up to date and support immune health.
- Arrange veterinary checks for active cats.
Vaccines protect against the pathogens they target; they do not prevent bacteria from a bite entering tissue. General advice about supporting immunity also does not replace wound examination and treatment. Neutering and providing safe outdoor access help reduce fights. Fighting between cats in the same home is also considered.
If your cat bites you or a scratch badly breaks the skin, seek advice from a healthcare professional yourself too. Avoid forcing a painful animal to be handled, and mention the risk of biting when booking the appointment.
This text provides general information and does not replace veterinary care. Contact a vet if your cat develops symptoms.
Frequently asked questions
Can an abscess heal when it bursts on its own?
Bursting can relieve pressure, but pus and damaged tissue may remain under the skin. Even a burst abscess needs veterinary assessment and proper cleaning.
Why is a small bite mark dangerous?
A narrow hole made by a tooth can reach deep into tissue and close rapidly at the surface. Bacteria left underneath can multiply even if only a small scab is visible on the skin.
Does every abscess need an antibiotic?
The need depends on the extent of infection and your cat's condition. Removing pus is an essential part of treatment, and your vet assesses what other medication is needed.
Why does an abscess return in the same place?
Remaining infection, a foreign object or a new bite may be responsible. Persistent or recurrent swelling is investigated so treatment can target its actual cause.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Abscesses in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Fight Wound Infections in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Care of Open Wounds in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Wounds and skin injuries, PDSA, accessed 2026-11-03.
- Skin lumps in cats, PDSA, accessed 2026-11-03.
- Feline Immunodeficiency Virus (FIV), Cornell Feline Health Centre, accessed 2026-11-03.
- Cat bite abscesses, PDSA, accessed 2026-11-03.