What Is Ringworm in Cats?
Despite its name, ringworm is not caused by a worm. It is a highly contagious fungal skin infection caused by dermatophyte fungi, most commonly Microsporum canis (responsible for more than 90 percent of feline cases), Trichophyton mentagrophytes, and Microsporum gypseum. The “ring” in the name refers to the circular, expanding skin lesion typical in humans — cats often show different patterns.
Dermatophytes feed on keratin, the protein found in skin, hair shafts, and nails. They colonize the outermost skin layers and hair follicle openings, causing local inflammation and hair loss.
Ringworm is zoonotic — meaning it can and does spread from infected cats to humans, particularly children, the elderly, and immunocompromised individuals. It can also spread to dogs and other household pets. For these reasons, ringworm in a household cat is a public health concern, not just a pet health issue, and prompt treatment and environmental decontamination are essential. HeiBob helps cat owners find experienced veterinary clinics for diagnosis and treatment guidance.
How Cats Get Ringworm
Dermatophyte spores are highly resilient — they survive in the environment for 12 to 24 months and are resistant to many common cleaning products. Transmission routes include direct contact with an infected animal, indirect contact through bedding, grooming tools, furniture, carpets, and clothing where spores persist, and soil contact for outdoor cats since Microsporum gypseum lives naturally in soil. Healthy adult cats with intact immune systems often resist infection even after exposure, or develop subclinical infection with no visible signs — but they can still shed spores and infect susceptible animals or people.
Signs and Symptoms in Cats
Feline ringworm does not always produce the classic circular lesion seen in people. Look for circular or irregular patches of hair loss most commonly on the face, head, forelimbs, and paws; broken hair shafts that leave a moth-eaten appearance; scaling or dandruff-like flaking at the base of the hair; mildly red inflamed skin at lesion edges; occasionally a severe form called kerion which is a raised boggy painful nodule that drains fluid; nail involvement causing thickened brittle deformed claws; and some cats show no visible signs but carry and shed spores prolifically.
A wood’s lamp (UV light) causes infected hairs to fluoresce a blue-green color with M. canis infections — but only about 50 to 70 percent of strains do this. Definitive diagnosis requires fungal culture (DTM — dermatophyte test medium) or PCR testing.
Treatment
Ringworm treatment requires both treating the cat and decontaminating the environment simultaneously — treating only the cat while spores persist at home guarantees reinfection. All cats in the household should be treated, even those without visible lesions.
Topical antifungals include lime sulfur dips, miconazole-chlorhexidine shampoos, and enilconazole spray applied twice weekly. Oral antifungals — itraconazole is the first-line systemic treatment — are typically given for 6 weeks or until two consecutive negative fungal cultures. For longhaired cats, clipping reduces the fungal burden on the coat.
Environmental decontamination requires vacuuming all surfaces daily, washing bedding in hot water, cleaning hard surfaces with dilute bleach (1:10 dilution) or accelerated hydrogen peroxide products, and discarding or disinfecting grooming tools. This process may need to continue for the duration of treatment — often 6 to 12 weeks.
Prevention and Household Management
Isolate newly adopted cats for 2 to 3 weeks and have them examined before introducing them to resident pets. Treat all in-contact cats in a household simultaneously. Wash hands thoroughly after handling any cat with unknown ringworm status. Do not share grooming tools between pets without disinfecting. Keep immunocompromised family members away from potentially infected cats during treatment.
Frequently Asked Questions
Can I get ringworm from my cat?
Yes. Microsporum canis readily infects humans. In people, ringworm typically appears as red, scaly, circular patches on the skin. Children, the elderly, and immunocompromised individuals are most vulnerable. If anyone in your household develops unexplained circular skin rashes while your cat is being treated, they should see a doctor.
How long does cat ringworm treatment take?
Treatment typically takes 6 to 12 weeks. Many cats look much better after 4 to 6 weeks, but it is essential to continue treatment until two fungal cultures taken 2 weeks apart are both negative. Stopping early is the most common reason for relapse.
Do I need to get rid of my cat if it has ringworm?
No. Ringworm is treatable and curable. Most cats are fully cleared with appropriate treatment. Abandoning the cat is not necessary or warranted.
What does ringworm look like on a cat vs. other conditions?
The patchy hair loss of ringworm can look like flea allergy dermatitis, mange, or stress-related overgrooming. The key distinguishing features are scaling at the follicle level and positive fungal culture. A vet examination is essential.
Can indoor-only cats get ringworm?
Yes. Humans can bring spores home on clothing or shoes from contact with infected animals elsewhere. Ringworm, while less common in indoor-only cats, is still possible.