Checking a cat for ringworm starts with a careful visual inspection of the skin and coat, focusing on the face, ear tips, tail, and feet, where infections most commonly appear. You’re looking for bald or thinning patches with scaly, crusted skin and broken-off hairs. But because some cats carry the fungus without obvious symptoms, a visual check alone isn’t always enough to confirm or rule out an infection.
What Ringworm Looks Like on a Cat
Ringworm in cats rarely produces the neat circular rash people get. Instead, you’ll typically see irregular patches of hair loss with dry, flaky, or crusty skin underneath. The hairs around the edges of these patches often look stubby or broken rather than cleanly missing. Run your fingers gently over your cat’s coat and feel for rough, scaly spots you might not immediately see, especially on darker fur.
Some cats develop a pattern called miliary dermatitis: small, solid bumps scattered across the skin that feel like tiny scabs or grains of sand when you pet them. These bumps tend to itch. Cats with more widespread infections can develop larger raised areas with open sores. The infection favors the face, ear tips, tail, and feet, so give those areas extra attention during your check. Look at the ear margins closely, since hair loss along the edges of the ears is a common early sign.
Keep in mind that ringworm can mimic other skin conditions. Flea allergies, bacterial infections, and even stress-related overgrooming can produce similar-looking bald patches. That’s why visual inspection is a useful first step but not a reliable diagnosis on its own.
Cats That Carry Ringworm Without Symptoms
Long-haired cats are especially tricky. They can harbor ringworm spores deep in their coat without developing any visible lesions. These subclinical carriers shed infectious hair fragments into the environment, which is how ringworm spreads through multi-cat households without an obvious source. If one cat in your home has confirmed ringworm, every other cat should be tested even if they look perfectly healthy. A visual check will miss these carriers entirely.
The Wood’s Lamp Test
A Wood’s lamp is a handheld ultraviolet light that causes certain ringworm species to glow. When used in a dark room, infected hair shafts produce a bright apple-green fluorescence along the shaft itself, not just on the skin surface. This test works well for the most common species in cats: over 90% of untreated cats naturally infected with it will fluoresce positive.
Your vet will likely use this as a first screening tool because it gives near-instant results. A few important caveats, though. Skin ointments, lint, and other debris can produce false glows that look white or blue-white rather than the distinctive apple green. And while most feline ringworm cases involve the species that fluoresces, less common fungal species won’t glow at all. A negative Wood’s lamp result doesn’t guarantee your cat is clear.
Microscopic Hair Examination
A vet can pluck hairs from a suspicious area and examine them under a microscope, a procedure sometimes called a trichogram. They’re looking for tiny fungal spores coating and penetrating the hair shaft. Infected hairs are fragile and tend to break easily, which is why you see those stubby, snapped-off hairs in affected patches. This test is quick and useful for initial screening, but it requires experience to interpret correctly and can miss early or mild infections where spore numbers are low.
Fungal Culture: The Gold Standard
If your vet wants a definitive answer, they’ll collect hair and skin samples and place them on a special culture medium. This is the most reliable way to confirm ringworm and identify the exact fungal species involved.
The downside is time. Fungal cultures can take up to 21 days to fully confirm a negative result, though positive growth typically shows up faster. In one study of shelter cats, over 93% of positive cultures produced identifiable growth within 7 days. So you may get a “yes” answer within a week, but a confident “no” requires patience.
The culture medium used in most clinics changes color when a ringworm species grows on it, shifting from yellow to red. Some pet owners purchase these culture plates online and attempt testing at home. While the plates themselves are the same product vets use, interpreting the results correctly is harder than it looks. Contaminant molds can also trigger a color change, leading to false positives. Timing matters too: you need to read the plate daily and note whether the color change happens simultaneously with colony growth, not after. If you go this route, photograph the plate daily and have your vet review the results.
PCR Testing for Faster Results
PCR testing analyzes hair and skin samples for fungal DNA rather than waiting for a live organism to grow. The turnaround time is only 1 to 3 days, a significant improvement over traditional culture. The tradeoff is higher cost. PCR is especially useful when you need a fast answer, for example, before introducing a new cat to your household or when managing an outbreak in a multi-cat home. Your vet sends the sample to an outside lab, so results aren’t available in the exam room the way a Wood’s lamp screening is.
A Practical Approach to Checking Your Cat
Start by examining your cat in good lighting. Part the fur section by section, paying close attention to the face, ears, paws, and tail. Look for any patches where hair is thinning, broken, or missing. Feel for scaly texture, small bumps, or crusty areas. Check the skin underneath the fur for redness or flaking.
If you find suspicious areas, or if your cat has been exposed to a known ringworm-positive animal, schedule a vet visit for proper testing. A typical diagnostic workup starts with a Wood’s lamp screening, possibly followed by a microscopic hair exam, and then a fungal culture or PCR test if results are inconclusive. No single test is perfect on its own, so vets often combine two or more methods to reach a confident diagnosis.
Ringworm spores are hardy and can survive in the environment for months, clinging to bedding, furniture, and carpet. If your cat tests positive, you’ll need to address both the animal and the living space to prevent reinfection or spread to other pets and people in the household.