Ringworm in cats is not a worm at all. It’s a fungal skin infection caused by organisms called dermatophytes that feed on keratin, the protein in skin, hair, and nails. The fungus responsible for the vast majority of feline cases is Microsporum canis. Despite sounding alarming, ringworm is treatable and curable, though it requires patience and consistent effort to fully clear from both your cat and your home.
Why It’s Called Ringworm
The name comes from the circular, ring-shaped patches of hair loss the infection often produces on skin. There is no worm involved. The fungus grows outward from a central point of infection, creating that characteristic round lesion as it spreads through the skin and hair follicles. That said, not every case looks like a neat circle. Some cats develop irregular patches, widespread flaking, or subtle signs that are easy to miss entirely.
What Ringworm Looks Like on a Cat
The most recognizable sign is circular areas of hair loss, often with broken, stubbly hair at the edges. The exposed skin may look scaly, crusty, or slightly red. Other common signs include changes in hair or skin color, dandruff, inflamed skin, and excessive grooming or scratching. Some cats develop infected claws or nail beds, which can cause the nails to become rough or misshapen.
Here’s what makes ringworm tricky: some cats, particularly long-haired breeds, can carry the fungus without showing obvious symptoms. They look perfectly healthy but shed fungal spores into the environment and onto other animals and people. Kittens and cats with weakened immune systems tend to show the most visible signs, while healthy adult cats sometimes fight off mild infections on their own or carry the fungus with minimal evidence.
How Cats Get Infected
Ringworm spreads through direct contact with an infected animal or through contaminated objects like bedding, brushes, furniture, and carpet. The fungal spores are remarkably hardy. They can survive in the environment for 12 to 20 months, which is why reinfection is such a common frustration for cat owners. Your cat doesn’t need to touch another infected animal directly. Simply lying on a couch or using a bed where spores have settled is enough.
Cats in shelters, catteries, or multi-cat households face higher risk because of close quarters and shared surfaces. Kittens are especially vulnerable, as are older cats and those on medications that suppress the immune system.
How Vets Diagnose Ringworm
A vet will typically start with a Wood’s lamp, which is an ultraviolet light. Over 90% of untreated cats naturally infected with M. canis will glow an apple-green color under this light. It’s a quick screening tool, but a negative result doesn’t rule out infection, since some fungal species and even some M. canis strains don’t fluoresce.
For a definitive answer, vets rely on one of two main tests:
- Fungal culture: Hair and skin samples are placed on a special growth medium. Most positive results appear within 7 days, though cultures are sometimes monitored for up to three weeks. This remains the gold standard for confirming infection.
- PCR testing: This DNA-based test identifies the fungus more quickly than culture. For M. canis, PCR has a sensitivity of about 86% and a specificity of nearly 98%, meaning it’s very reliable when it returns a positive result but can occasionally miss an infection.
Your vet may use a combination of these methods, especially if your cat’s symptoms are ambiguous or if you have multiple pets at home that need screening.
Treatment: What to Expect
Treating ringworm involves attacking the fungus on two fronts: on your cat and in your home. Skipping either one almost guarantees the infection will come back.
Treating Your Cat
Most cats need both topical and oral antifungal treatment. Topical treatment usually means medicated baths or dips, sometimes combined with antifungal creams or ointments applied directly to lesions. These help reduce the number of spores your cat sheds into the environment.
Oral antifungal medication does the heavier lifting by clearing the infection from within the hair follicles and skin. One common protocol uses an oral antifungal solution given daily on a pulsing schedule: one week on, one week off, repeated for three cycles over about five weeks. Your vet will choose the specific medication and schedule based on the severity of infection and your cat’s overall health.
Treatment typically continues until your cat produces at least two consecutive negative fungal cultures, spaced a few weeks apart. For most cats, this process takes somewhere between 6 and 12 weeks total, though stubborn cases can run longer. Visible improvement often starts within a few weeks, but stopping treatment early because your cat “looks better” is one of the most common reasons for relapse.
Cleaning Your Home
Because fungal spores can persist for well over a year on surfaces, environmental decontamination is not optional. Focus on areas where your cat spends the most time. Vacuum carpets, furniture, and fabric surfaces frequently, and dispose of the vacuum bag or empty the canister outside. Wash bedding, blankets, and removable covers in hot water.
Hard surfaces can be disinfected with a diluted bleach solution. A 1:10 bleach-to-water ratio is sometimes cited, but shelter medicine guidelines note that this concentration is harsher than necessary for routine use. Your vet can recommend an appropriate disinfectant and dilution for your situation. The key is consistent, repeated cleaning throughout the treatment period, not just a single deep clean.
Confining your cat to one easily cleaned room during treatment can make the decontamination process far more manageable, especially in larger homes or homes with carpet throughout.
Can You Catch Ringworm From Your Cat?
Yes. Ringworm is zoonotic, meaning it passes between animals and humans. On human skin, it typically appears as an itchy, red, ring-shaped rash that may be scaly, cracked, or slightly raised. It can show up anywhere on the body but commonly appears on the face, arms, and legs. The area around the rash may develop hair loss, and in more severe cases the rash can become crusted or filled with pus.
Children, older adults, and people with weakened immune systems are most susceptible. If your cat has been diagnosed with ringworm, wash your hands thoroughly after handling them, avoid letting them sleep on your bed, and watch for any skin changes on yourself or family members. Human ringworm is treatable with over-the-counter antifungal creams in mild cases, though more extensive infections may need prescription medication.
Which Cats Are Most at Risk
Ringworm accounts for less than 4% of all feline skin disorders, so it’s not as common as many owners assume. However, certain cats face a disproportionate risk:
- Kittens: Their immune systems are still developing, making them more vulnerable to infection and more likely to show severe symptoms.
- Long-haired breeds: Persians and Himalayans are particularly prone. Their dense coats may trap spores more easily and make infections harder to detect visually.
- Immunocompromised cats: Those with FIV, FeLV, or cats on long-term corticosteroids have less ability to fight off the fungus naturally.
- Shelter and multi-cat household cats: High-density living creates more opportunities for exposure and makes environmental decontamination harder.
Living With a Ringworm-Positive Cat
The weeks of treatment can feel tedious, but the prognosis is excellent. Most cats recover fully with no lasting skin damage. The biggest challenges are sticking with the full course of medication, keeping up with environmental cleaning, and being patient enough to wait for those negative cultures before declaring victory. If you have other pets in the home, your vet may recommend testing or prophylactically treating them even if they aren’t showing symptoms, since asymptomatic carriers can silently keep the cycle going.