Here is the uncomfortable part nobody tells you: some of the skin problems your cat picks up are not just their problem. Most of the little bumps, scabs, and thin spots you find while petting a cat are harmless and will sort themselves out. But a small set of fungal infections are contagious, and a few of those can move from your cat’s skin to yours. That is the real reason it is worth learning to read a cat’s coat, and it is the difference between a spot you can watch and one that needs a vet and a lab test.
Fungi that infect a cat’s skin come from three places: other animals, the soil, and the yeast that already live quietly on healthy skin. Which ones can actually cause trouble depends on your cat’s breed, where you live, the local environment, and how strong their immune system is. So the goal is not to memorize every fungus. It is to recognize the pattern that says “this is fungal, and it may not stay on the cat.”
What a fungal spot actually looks like
Fungal lesions tend to share a look. You are usually seeing a crusted, scaly, reddened, hairless area, often roughly circular, with broken or brittle hairs fringing the edge. On many cats these turn up first around the face, then spread to the paws and body. Most cats find them itchy. That circular, flaky, balding signature is the thing to notice, because it does not describe a bug bite or a scratch, and it is worth taking seriously rather than waiting out.
One breed-specific wrinkle: Persians sometimes develop firm nodules under the skin instead of the usual flat, scaly patches, so the classic ring may not appear at all.
The two you are most likely to meet
Ringworm
Despite the name, ringworm has nothing to do with worms. In cats it is caused by a few fungi, most commonly Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes. It usually passes by direct contact with an infected animal or person through an open lesion, though contaminated soil or bedding can carry it too. Lesions show up one to three weeks after exposure.
To confirm it, vets rely on a fungal culture, typically collected by brushing the coat with a brand-new toothbrush and pressing the brush onto a fungal growth medium. You may also see a vet reach for a Wood’s lamp, since some ringworm fungi fluoresce under black light. It is a handy screen, but it is not proof either way, because plenty of things cause false positives and false negatives.
In an otherwise healthy cat, ringworm often clears on its own eventually. Treatment is still recommended, both to speed things up and because it is contagious to you and to other pets in the house. The standard approach pairs a topical antifungal (a medicated dip or shampoo) with an oral antifungal.
“Ringworm is the case where ‘let’s wait and see’ actually costs you, because every day it’s active is another day it can spread to the other cat or to you,” says Dr. Nina Kohl. “Treating the cat and cleaning the house are one job, not two, and skipping the cleaning is how families end up passing it back and forth for months.”
Decontaminating the environment matters as much as treating the cat. Vacuum and brush surfaces to lift away loose hair and skin flakes, steam-clean carpets and upholstery where practical, and wash bedding and washable fabrics in a dilute bleach solution following the CDC’s ringworm guidance. And set your expectations: fungi grow slowly and die slowly, so a full clearance takes weeks to months.
Malassezia dermatitis
Malassezia yeast are a normal resident of feline skin. Trouble starts when they overgrow, leaving skin itchy and flaky, often with a greasy, reddish-brown discharge or discoloration. This overgrowth tends to appear in cats whose defenses are down, such as those with feline immunodeficiency virus, feline leukemia virus, diabetes, cancer, or other underlying illness. Coat type plays a role too: hairless breeds like the Sphynx and Devon Rex can be prone to a generalized version, while very fluffy breeds like Persians and Himalayans tend to get it in their facial folds.
Because the yeast live on the skin’s surface, treatment is topical. A medicated shampoo handles widespread cases, and cats with a small, localized patch often do well with medicated wipes.
The rare, scarier ones from the soil
Outdoor cats meet a wider world of pathogens, and some of the fungi in soil cause genuinely serious disease. This is one more quiet argument for keeping cats indoors, no matter how badly they want to befriend the bird on the patio.
Cryptococcosis. Cryptococcus lives in soil. When a cat stirs up contaminated dirt and inhales the spores, the infection can go systemic and produce soft-to-firm masses around the body. The most recognizable outward sign is a badly swollen, hairless, ulcerated tip of the nose.
Sporotrichosis. Sporothrix fungi cause one or several nodules that start firm, then soften and drain pus. In bad cases the yeast spreads through the lymphatic system into systemic disease. Cats pick it up when something carrying contaminated soil punctures their skin, which is why the human version is nicknamed “rose gardener’s disease” after thorn pricks.
Blastomycosis. Like the others, Blastomyces lives in soil and turns serious when spores are inhaled. Infected cats can develop skin lesions ranging from small nodules to large abscesses. It is a severe, life-threatening systemic illness, though fortunately uncommon in cats.
So, can you catch it?
Some of these, yes. People get ringworm through direct contact with an infected cat. Sporothrix can also pass straight from cat to human, often through a scratch. The systemic soil fungi behind cryptococcosis and blastomycosis affect people too, but the form an infected cat carries does not transmit directly to you. Either way, the sensible habit is the same: practice good hygiene and wash your hands after handling any cat, and especially one with skin lesions.
What newer research adds
The cat-to-human angle on sporotrichosis is not just a Brazil story anymore. In 2022, U.S. researchers documented a cluster of feline sporotrichosis in Kansas that included a confirmed infection in a veterinary technician who had handled a sick cat, later written up in the CDC’s Emerging Infectious Diseases journal. The takeaway for cat owners is not alarm, it is awareness: the highly transmissible Sporothrix brasiliensis strain driving large outbreaks in Latin America has not been detected in the United States, and cat-to-person spread of the strain that is here remains rare.
What that means at home is simple. If your cat develops firm lumps that open and drain, especially after outdoor roaming, treat it as a reason to see the vet promptly and to mention any sores of your own to your doctor. Early recognition is what keeps a rare problem from becoming your problem.
When to call the vet
Book a visit rather than waiting if you see a circular, crusty, or hairless patch, especially one that is spreading or itchy; any firm lump that softens and drains; a swollen, ulcerated nose; or new skin lesions in a cat who is also unwell, elderly, or known to have a condition like FIV, feline leukemia, or diabetes. And call your own doctor if you develop a red, ring-shaped, scaly rash after handling a cat with a skin problem.
References
- Moriello, K. A., et al. “Diagnosis and Treatment of Dermatophytosis in Dogs and Cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology.” Veterinary Dermatology, 2017. Link
- Centers for Disease Control and Prevention. “Ringworm Prevention.” Link
- Rojas, F. D., et al. “Sporotrichosis Cluster in Domestic Cats and Veterinary Technician, Kansas, USA, 2022.” Emerging Infectious Diseases, CDC, 2024. Link
- Cornell Feline Health Center. “Ringworm.” Link
