Ringworm on a cat typically appears as circular patches of hair loss with scaly, crusty skin underneath. Despite the name, it’s not a worm at all. It’s a fungal infection that lives on the outer layer of skin and in hair follicles, and it has a distinctive look once you know what to watch for.
The Classic Signs
The most recognizable feature is a roughly circular bald spot where fur has broken off or fallen out. The remaining hair in and around the patch often looks stubbly, as if it snapped rather than shed naturally. The exposed skin beneath is usually scaly or flaky, sometimes with a thin crust on top. You may also notice redness, changes in skin color (darker or lighter than surrounding skin), or small raised bumps.
Not every case looks textbook, though. Ringworm can produce any combination of hair loss, scaling, crusting, redness, small bumps, darkened skin, and dandruff. Some cats develop a single well-defined circle. Others get multiple irregular patches that don’t look circular at all, or just generalized flaking that resembles dry skin. The amount of itching varies too. Some cats scratch and overgroom the area obsessively, while others seem completely unbothered.
Where It Shows Up First
Ringworm tends to appear on the face, ear tips, tail, and feet. These are areas where cats come into contact with contaminated surfaces or other animals, making them the usual entry points for the fungus. Lesions can spread to the legs, back, or belly over time, especially if left untreated. In some cats the infection also reaches the claws or nail beds, causing them to look rough, flaky, or misshapen.
How It Changes Over Time
Early ringworm is easy to miss. You might notice a small area where the fur looks thinner or slightly broken, or a patch of skin that seems a little flakier than usual. At this stage it can look like nothing more than a minor scratch or a spot where your cat rubbed against something.
As the fungus spreads outward from the initial infection site, the bald patch grows and the edges become more defined. The outer ring of the lesion is often the most inflamed, with the center sometimes appearing calmer or starting to heal. This expanding-ring pattern is what gives “ringworm” its name. Over weeks, untreated patches develop thicker crusts, more pronounced scaling, and the hair loss becomes impossible to overlook. Multiple spots can merge into larger irregular areas of baldness.
Cats That Show No Signs at All
Some cats carry the ringworm fungus on their coat and are fully contagious without ever developing a single visible lesion. Longhaired breeds are particularly prone to being asymptomatic carriers. Their dense coats can harbor infected hairs that shed fungal spores into the environment, yet the skin underneath looks normal. This is one reason ringworm spreads so efficiently in multi-cat households and shelters: the cat responsible may not look sick.
If another pet or a person in your home develops ringworm and you can’t find any lesions on your cat, the cat may still be the source. A veterinary test is the only way to confirm or rule out a carrier.
How Vets Confirm Ringworm
Visual inspection alone isn’t reliable because several other skin conditions (bacterial infections, mites, allergies) can mimic ringworm’s appearance. Vets typically start with a Wood’s lamp, which is an ultraviolet light. Some strains of the ringworm fungus cause infected hairs to glow a fluorescent green under this light. If hairs glow, a vet can examine them under a microscope to look for fungal spores right away.
When lesions look suspicious but don’t glow, a fungal culture becomes especially important. The vet brushes a sterile toothbrush over the cat’s coat and presses it onto a culture plate. If ringworm is present, colonies typically start growing within 7 to 10 days, though labs hold the plate for a full 21 days before calling it negative. The culture also gives quantitative information: the number of fungal colonies that grow (scored from P1, meaning 1 to 4 colonies, up to P3, meaning 10 or more) tells the vet how heavy the infection is. PCR testing is another option that returns a simple positive or negative result faster, but it doesn’t measure the level of infection the way a culture does.
What It Looks Like on Humans
Ringworm passes easily from cats to people, so if your cat has a suspicious patch, check your own skin too. On human skin the infection produces the classic red ring: a circular rash with a raised, scaly border and clearer skin in the center. It’s usually itchy. The spots most commonly appear on the arms, hands, or anywhere you’ve had direct contact with the cat. If you notice a ring-shaped rash developing while your cat has bald, scaly patches, it’s a strong clue that ringworm is the culprit for both of you.
Signs That Healing Has Started
Once treatment begins, the first thing you’ll notice is that existing patches stop expanding and no new ones appear. The crusting and scaling gradually diminish, and the redness fades. Fine, short hairs start growing back in the center of bald spots. Full regrowth takes time, often several weeks to a couple of months, and the new fur may initially look slightly different in color or texture before blending in with the rest of the coat.
It’s important not to stop treatment based on appearance alone. A cat can look fully healed while still carrying the fungus. Vets typically confirm clearance with follow-up cultures rather than relying on how the coat looks, because a cat that tests positive is still shedding spores and can reinfect other animals or people in the home.