However, not every pus-filled skin lump is furunculosis. Deep inflammation beginning in a hair follicle, a bite abscess and other diseases causing lumps can look similar. Treatment is chosen according to the confirmed cause and depth of damage.
When to see a vet urgently
Seek urgent assessment if general health deteriorates alongside a local skin lesion:
- Your cat is very lethargic, does not eat or withdraws unusually.
- Swelling spreads rapidly or the area is very painful.
- Your cat has laboured breathing, collapses or cannot stand.
Do not wait for a painful pus-filled lesion to burst. You can find a vet near you.
Overview
A furuncle, or boil, is an inflammatory focus that forms around a hair follicle. It usually appears as a painful lump that gradually enlarges and fills with pus. As it matures, it bursts and releases pus. Furunculosis can occur on a cat's face, neck, back, tail and areas where the skin rubs.
More precisely, the hair follicle wall may rupture in furunculosis. Keratin, the horny material within the follicle, enters surrounding tissue and sustains inflammation. This occurs in complicated feline chin acne, for example. Blackheads may appear first, followed by painful swelling and discharging lesions.
Abscess is a broader term for a pus-filled cavity and does not have to begin in a follicle. A bite can introduce bacteria directly beneath the skin. Different background information is therefore sought for similar-looking lesions. An abscess bursting also does not guarantee that the cavity has emptied or the cause has gone.
Causes
Factors causing furunculosis in cats include:
- Bacterial infection, most often staphylococci.
- Skin injuries, scratches and bites.
- Soiling of the coat and skin.
- Parasites, such as fleas and mites, causing itching and scratching.
- Hormonal diseases, including diabetes and other endocrine disorders.
- Reduced immunity and chronic diseases.
Bacterial skin infection is less common in cats than in dogs. Recurrent infections prompt a search for causes of skin damage or poor healing. Scratching and licking can break the skin barrier, so the source of itching is also investigated.
The bacterial species cannot be identified from a lump. Bite abscesses in particular may involve different bacteria from follicle inflammation. Nor does every hormonal disorder carry the same risk in cats. Underlying disease is suspected according to symptoms and findings, rather than starting hormone treatment based on a skin lesion alone.
Risk factors
- Cats with long or dense coats.
- Obese cats, with skin folds and reduced grooming.
- Older cats and those in poor condition.
- Cats with chronic skin inflammation or allergies.
- Poor hygiene.
Information on precise risk factors for feline furunculosis is limited. A long coat or one pus-filled lump does not establish poor hygiene. However, changes hidden beneath fur can go unnoticed, so painful or discharging areas are examined regardless of coat type.
Typical symptoms
Signs of furunculosis in cats include:
- Firm, painful lumps beneath the skin.
- Redness and swelling around lesions.
- Pus-filled lesions that burst over time.
- Hair loss over the inflammatory focus.
- Tenderness to touch.
- In severe cases, multiple abscesses, fever and lethargy.
Only a wet patch, crusts or stuck-together hairs may be visible on the coat despite deeper skin damage. Pain may appear as moving away or resisting stroking or lifting. Some cats constantly lick the area. Also record changes in appetite, activity and other skin areas.
A tract repeatedly draining from the same place may suggest that the original cause remains. A foreign object retained in tissue, for example, can sustain an abscess. Recurrence therefore does not always mean simply giving the same medicine again.
Complications and consequences
Untreated furunculosis can lead to:
- Spreading infection, including phlegmon and abscesses.
- Sepsis, sometimes called blood poisoning.
- A chronic form with continual new abscesses.
- Scarring and baldness at the affected site.
Sepsis is a severe response to infection that disrupts organ function. It differs from a pus-filled lesion alone or finding bacteria in a sample. Not every local skin infection progresses to sepsis, but a clear decline in general health needs prompt assessment.
Diagnosis at the vet
- Clinical examination.
- Bacterial culture of pus to select a suitable antibiotic.
- Cytology.
- A complete blood count in extensive or chronic cases.
- Ruling out parasites and fungal diseases.
The vet establishes where the lesion began, whether the skin itched before lumps formed, and whether your cat has fought or been injured. Report previous antibiotics, topical creams and treatment response. Early photographs can also help if the skin looks different at examination.
Cytology looks for inflammatory cells, bacteria, yeasts and other abnormal cells. Culture results are considered alongside this finding: a skin surface sample does not always represent a deep infection. Your vet chooses a suitable sampling site and assesses the need for susceptibility testing. Do not start leftover antibiotics before examination.
Unusual, persistent lumps or those that do not respond to appropriate treatment may need a skin biopsy. Less common bacteria, such as mycobacteria, can also cause similar draining nodules. They are not assumed to cause an ordinary abscess, but suspicion affects sample selection and laboratory testing. Investigating parasites and fungal infections may also require several samples.
Treatment
Treatment aims to remove both infection and the factor sustaining inflammation. Deep bacterial skin infection may require an oral antimicrobial chosen according to findings and susceptibility testing where necessary. A surface product alone may not reach deep inflammation. Itching, parasites or another confirmed underlying disease are treated at the same time.
A pus-filled cavity may need opening, draining and flushing. Any foreign object found is removed. The procedure and possible sedation are planned according to pain and lesion location. Pain relief is part of treatment; your cat does not have to endure painful handling by force.
A tidier skin surface does not always mean a deep lesion has healed. Planned follow-up assesses pain, discharge, lumps and new lesions. Medicine changes are agreed with the treating vet. If the response is poor, the diagnosis and need for samples are reassessed.
Home care
Do not pierce a lump with a needle or squeeze it. Clean the wound and surrounding skin only with a product prescribed for your cat, following the instructions. Tell the practice if handling causes severe pain or a medicine seems to irritate the skin. Treatment may need adapting so it can be carried out successfully.
Licking a topical product may be harmful. Agree how to prevent medicine licking and further skin damage. Also follow product handling instructions, such as wearing gloves and protecting the eyes. Do not add other creams or cleaning agents based on your own judgement.
Monitor eating and drinking and whether pain and swelling decrease. Contact the practice if discharge increases, new lumps appear or your cat does not start improving. A photograph can help track change, but does not replace examination when general health worsens.
Prognosis
A local bacterial infection may have a good prognosis when the pus-filled lesion is treated and its cause controlled. Recurrence risk rises if the factor sustaining inflammation remains. Finding an unusual pathogen or systemic disease can change both treatment needs and prognosis.
Prevention
- Care for your cat's coat and skin regularly.
- Maintain external parasite control for fleas and mites or ticks.
- Treat wounds and scratches promptly.
- Feed a varied diet to support immunity and skin health.
- Prevent and treat hormonal and chronic diseases.
Variety does not mean constantly changing foods or giving vitamin supplements. A complete diet meeting your cat's needs is the nutritional foundation; supplements do not automatically help, and excess intake can be harmful. Adding to the diet alone does not treat a pus-forming skin lesion.
To prevent bite injuries, reduce situations in which your cat gets into fights. Have a new wound checked, particularly if swelling, pain or discharge develops. Managing an itchy disease helps reduce further damage from scratching.
Important for cat owners
Furunculosis is more than a cosmetic problem: it causes pain and can spread infection. Remember never to squeeze abscesses yourself, because this can worsen inflammation and cause complications. Take your cat to a vet for diagnosis and treatment when you first notice pus-filled lumps.
This article provides general information and does not replace veterinary care. Contact a vet if you notice signs of illness in your cat.
Frequently asked questions
Is every cat abscess furunculosis?
No. Furunculosis involves deep hair follicle damage. A bite, for example, can cause a pus-filled cavity beneath the skin without inflammation beginning in a follicle.
Can a burst abscess be left untreated?
Do not assume it has healed. Pus or the factor sustaining inflammation may remain in the cavity. Your vet assesses cleaning, medicines and follow-up needs.
Is bacterial culture always needed?
The need depends on depth, previous treatment and recurrence. Culture helps identify bacteria and choose a medicine, but the sample must represent the lesion being treated.
Why does a lump return in the same place?
A remaining pus-filled cavity, foreign object or another skin disease may be responsible. A recurrent lesion is examined again rather than repeating earlier medicines yourself.
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
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