Lumps and bumps on cats: what every pet parent should know

Finding an unexpected lump on your cat can be alarming. The instinct to hope it’s nothing is understandable, but lumps have a wide range of causes, and there’s no reliable way to tell them apart without a vet’s help. Getting any new lump checked promptly is always the right call.

This guide covers the most common causes of lumps in cats, how vets investigate them, what treatment may involve, and what you can do at home to stay on top of your cat’s skin health.

Table of contents

• Common causes of lumps in cats
• How vets may investigate lumps
• Treatment options
• Reducing the risk
• How pet insurance can support your cat’s wellbeing

Common causes of lumps in cats

Trauma

Injuries from accidents, dog or cat fights, or other physical impacts like falls, can cause serious injuries to your cat and may look like swelling and lumps.

If your cat has been involved in an accident or other traumatic incident, always take them to your vet or local emergency clinic immediately, as some serious injuries may be hidden to the naked eye and need vet assessment.

Parasites

Flea and tick bites can trigger localised skin reactions that feel like small bumps. Ticks that are still attached to your cat can feel like a hard bump. In parts of Australia, paralysis ticks are a particular concern. Their toxin can be fatal without urgent vet treatment, even after the tick has been removed. If you find a tick on your cat, it’s important to remove it quickly and safely to reduce the risk of tick-borne disease or paralysis. A vet can help you remove a tick safely and perform any required health checks or testing following a tick-bite.

Never apply a parasite prevention product formulated for dogs to a cat, as these can be toxic to cats and can be deadly.

Speak to your vet to make sure your cat is covered by all the necessary parasite prevention products.

Allergies and inflammation

Allergic reactions to insect bites, stings, or other environmental triggers like food, grass, or pollens, can produce welts, hives, or small lumps on the skin. Your cat may find these to be very itchy. Contact your vet immediately if your cat seems to be having an allergic reaction, as anaphylaxis (a severe allergic reaction) can be life-threatening.

Some cats can also get ‘feline acne’, a condition often triggered by allergies, which causes the hair follicles on a cat’s chin to become clogged, irritated, and sometimes infected. This condition can appear like a dirty chin, or like black or dirty bumps on the chin and around the mouth.

Less commonly, cats can also develop a condition called ‘eosinophilic granuloma complex’, triggered by allergic or immune responses, which causes lumps and ulcers to appear on the lips or elsewhere on the body.

Infection (abscesses)

Abscesses are among the most common lumps seen in cats. They form when bacteria enter through a bite or scratch, typically during a fight, and develop into painful, pus-filled swellings. Cats with outdoor access are at higher risk. Abscesses are often accompanied by fever, loss of appetite, and lethargy, and need prompt vet treatment.

Foreign objects such as grass seeds lodged in the skin can also cause inflammation and infection, or abscesses. Sometimes grass seeds can travel underneath the skin, making them difficult to locate, or can get stuck in the paws, ears, eyes, and nose.

Tumours

Tumours arise when cells lose normal growth regulation. Tumours can either be benign or malignant. Benign tumours grow locally and don’t spread throughout the body. However, they can still cause problems in the local area if they grow too large. Malignant tumours are what most people understand as ‘cancer’; these tumours may cause significant problems in the local area of the body and can spread throughout the body, making your cat very unwell.

Tumours can grow slowly or quickly and may sometimes look like other types of lumps. Any lump of unknown origin should be assessed by a vet without delay.

How vets may investigate lumps

Your vet will ask a few questions around the history of the lump, including when you first noticed it and whether it has grown, and will then carry out a physical examination.

If you notice a new lump on your cat, it’s helpful to make a note of the date you first noticed it, how big it is, whether your cat is trying to lick or scratch the area, and whether you’ve noticed your cat has had any other changes in their behaviour, such as changes to their energy levels, appetite, or toileting.

Depending on what your vet finds, a fine needle aspirate (FNA) may be performed. This is where a small needle is used to take a sample of cells from the lump. The sample is spread onto a slide and examined under a microscope. Sometimes, this test can diagnose the lump. In other cases, the slide is sent to a specialist vet pathologist.

Other tests may also be recommended, such as blood tests, which can provide useful information on your cat’s health. For some lumps, a tissue biopsy under general anaesthesia may be required.

Treatment options

Treatment depends entirely on what the lump turns out to be. Some lumps may require medications, such as antibiotics, antifungals, or anti-inflammatory drugs. Others may require topical treatments, such as medicated creams, washes, or gels.

Sometimes a lump will require surgery, or referral to a specialist for ongoing treatment. And in some cases, a benign lump may simply be monitored over time rather than treated immediately.

Reducing the risk

Keeping your cat contained to your property, with supervised or enclosed outdoor access, reduces the risk of fight wounds and road accidents. Having female cats desexed before four months of age also significantly reduces the likelihood of mammary cancer later in life.

The most practical thing you can do is check your cat’s skin regularly, ideally during grooming sessions, and make sure they have regular vet health checks. Knowing what feels normal makes it much easier to notice something that doesn’t. The earlier a lump is found and assessed by a vet, the more treatment options are likely to be available.

How pet insurance can support your cat’s wellbeing

Diagnosing and treating lumps in cats can involve tests, biopsies, surgery, and follow-up care. Those costs can accumulate quickly, particularly when the lump turns out to need more complex treatment. Pet insurance helps manage those unexpected expenses, giving you the confidence to seek care without delay.

With RSPCA Pet Insurance, your policy also contributes to the RSPCA’s animal welfare work across Australia. To learn more about how RSPCA Pet Insurance could support you and your pet, click here. Or, if you’re ready to take the next step, you can fetch a commitment-free pet insurance quote online.

Disclaimer

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