Cats get cysts when skin glands or hair follicles become blocked, trapping fluid, keratin, or other material beneath the skin’s surface. Most feline cysts are benign, meaning they aren’t cancerous, but they can vary widely in size, texture, and location depending on what type of tissue is involved. Understanding why these lumps form can help you figure out whether the bump you’ve found on your cat needs attention or is simply a harmless quirk of aging skin.
How Cysts Form in Cat Skin
A cyst is essentially a small pocket that fills with material the body can’t expel on its own. In cats, the most common trigger is a malfunction in the hair follicle or one of the tiny glands embedded in the skin. Every hair follicle is surrounded by glands that produce oils and other secretions. When the duct leading out of one of these glands gets blocked, the gland keeps producing material with nowhere to go. Over time, that trapped material stretches the surrounding tissue into a fluid-filled or solid lump.
The blockage itself can happen for several reasons. One proposed mechanism is a problem with how skin cells harden and layer inside the gland’s duct, essentially creating a plug. In some cases, the immune system may also play a role, attacking the gland and triggering inflammation that narrows or seals the duct. Trauma, chronic skin irritation, or infection can all contribute to this process, though many cysts appear without any obvious external cause.
Types of Cysts Cats Develop
Not all cat cysts look or feel the same. The type depends on which structure in the skin is affected and what fills the cyst cavity.
Keratin-Filled Cysts
These cysts contain keratin, the tough protein that makes up hair and the outer layer of skin. They feel hard or solid to the touch and are often the same color as your cat’s fur. Most are caused by malformations of hair follicles. They can appear as a single lump or in clusters, though they’re only occasionally seen in cats compared to dogs. These cysts are benign.
Sweat Gland Cysts
Cats have a type of sweat gland (apocrine glands) distributed across their skin, and these glands can develop fluid-filled cysts. This type shows up most often in middle-aged or older cats and tends to appear on the head and neck. They look like small blisters or fluid-filled bumps under the skin. Some cats develop a single cyst, while others develop a more widespread form where glands associated with many hair follicles become dilated at once. These are also benign.
Hair Follicle Tumors That Look Like Cysts
Some growths originating from hair follicles can closely mimic cysts. The benign forms appear as lumps ranging from about half an inch to two inches across, sitting in the deeper layers of the skin. If these expand or if your cat scratches at them, they can ulcerate and ooze a thick, yellowish, cheese-like material. Despite the alarming appearance, the benign versions aren’t dangerous, but they do need a vet’s evaluation to rule out a malignant form.
Dilated Pore Cysts
This rare type occurs only in elderly cats. It looks like an oversized blackhead: a single, dome-shaped bump, sometimes with a plug of keratin poking out from the surface that can resemble a small horn. These are benign and can be permanently cured with surgical removal.
Age, Breed, and Other Risk Factors
Age is the single biggest risk factor. Sweat gland cysts are largely a condition of middle-aged and older cats, and dilated pore cysts appear exclusively in aged cats. As skin ages, gland function changes, ducts narrow, and the likelihood of blockages increases.
Genetics can also play a role, though specific breed predispositions for common skin cysts are less well-documented in cats than in dogs. One inherited condition worth knowing about is cutaneous asthenia, a group of syndromes involving defective collagen production. Cats with this condition, which has been identified in Himalayans and domestic shorthairs, develop unusually fragile, stretchy skin that’s prone to forming fluid-filled sacs and cysts. In Himalayans the trait is recessive (both parents must carry it), while in some domestic shorthair lines it’s dominant (only one parent needs to carry it).
What a Cyst Looks and Feels Like
Most cysts present as a round, well-defined lump just beneath the skin’s surface. Fluid-filled cysts feel soft and compressible, somewhat like pressing on a small water balloon. Keratin-filled cysts feel firmer, almost like a pebble under the skin. The overlying fur and skin usually look normal unless the cat has been licking, biting, or scratching at the area.
Location can offer a clue about the type. A fluid-filled bump on the head or neck in an older cat is likely a sweat gland cyst. A hard, hair-colored lump anywhere on the body could be a keratin cyst. But feel and location alone can’t confirm whether a lump is a harmless cyst or something more concerning. A vet will typically use a fine needle to draw out a small sample of the contents, which is a quick, minimally invasive way to identify what’s inside.
When a Cyst Becomes a Problem
Most cysts sit quietly under the skin without causing pain or health issues. They become a concern in a few specific situations.
Infection is the most common complication. If bacteria get into a cyst, whether through a scratch, a bite wound, or the cyst rupturing on its own, it can develop into an abscess. An infected cyst or abscess typically appears as a sudden, painful swelling that may feel firm or squishy. The skin over it often turns red. If the abscess ruptures, it discharges thick, foul-smelling liquid. Cats with an abscess frequently develop a fever and become lethargic, withdrawn, or lose their appetite, even after the abscess has drained.
Rapid growth is another red flag. A cyst that was stable for months and suddenly starts expanding deserves prompt evaluation. So does any lump that feels fixed to deeper tissue rather than sliding freely under the skin, or one that develops an irregular shape. These features don’t necessarily mean cancer, but they warrant a closer look to rule it out.
How Cysts Are Treated
Small, stable, clearly benign cysts often don’t need any treatment at all. Your vet may recommend simply monitoring the lump over time, checking at regular visits to make sure it hasn’t changed in size or character.
Surgical removal is the definitive treatment when a cyst is bothersome, infected, growing, or in a location where it’s causing your cat discomfort. For most skin cysts, this is a straightforward procedure: the entire cyst wall is removed so it can’t refill. Dilated pore cysts, for example, are considered cured once fully excised. If only the contents are drained without removing the cyst wall, the cyst will almost always refill over weeks to months.
For infected cysts that have progressed to abscesses, treatment typically involves draining the infection and a course of antibiotics. Cats that are feverish, dehydrated, or not eating may need more supportive care to recover fully. The key thing to avoid at home is squeezing or popping a cyst yourself. This can push material deeper into surrounding tissue, introduce bacteria, and turn a harmless lump into a painful infection.