Glossary

Ringworm

A contagious fungal infection of skin, hair and claws that causes patchy hair loss and can spread to people and other pets.

Also called: dermatophytosis, Microsporum canis, cat fungal skin infection

Ringworm is not caused by a worm. It is a fungal infection, most often by Microsporum canis, that grows in the outer layers of skin, hair and claws. The name comes from the round, red rings it makes on people. In cats it is less obvious: scaly patches of hair loss, broken hairs, crusting or sometimes no visible signs at all. Kittens, longhaired cats and cats from shelters or catteries get it most often.

The fungus spreads by direct contact and through spores that cling to bedding, brushes, furniture and carpets and can last for many months. People can catch it, and children, older adults and those with weak immune systems are most likely to. If a person develops an itchy, ring-shaped rash after contact with an infected cat, they should see a doctor.

A vet confirms ringworm with a fungal culture, a PCR test, or by looking at hairs under a special light and a microscope. Treatment takes weeks, covers the cat and its surroundings, and may include medicines by mouth or washes. Cats can look better well before they are cured, so follow the vet's retest plan. Ask your vet how to isolate the cat and clean the home.

Last reviewed November 7, 2026

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Related terms

Flea allergy dermatitis An itchy skin disease caused by an allergic reaction to flea saliva, where even a few bites trigger scabs and hair loss. Feline acne A skin condition that shows as blackheads and sometimes sores on a cat's chin and lower lip. Wellness exam A routine vet visit for a healthy-looking cat to check its body, update vaccines and parasite control, and catch problems early. Ear mites Tiny surface parasites that live in a cat's ear canal and cause itching and dark, crumbly debris.

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