How long is ringworm contagious?

Ringworm (which is a fungus, not a worm) stays contagious as long as the infection is active. Untreated, that can be weeks to months, with the fungus spreading to other people, other body parts, and shared items the whole time. Once you start an effective antifungal, contagiousness drops fast: the standard guidance is that it is no longer considered contagious about 48 hours after starting treatment. How it spreads, per the CDC: skin-to-skin contact with infected people or animals (cats and dogs are common sources), shared items like towels, bedding, clothing, hairbrushes, and sports gear, and surfaces in locker rooms and showers. The practical containment list while contagious: cover the rash, no sharing towels or clothing, wash hands after touching it, keep feet covered in shared showers and locker rooms, wash bedding and clothes hot, and check household pets for bald patches (a vet visit if found, since reinfection ping-pong between pet and human is common). Treatment: over-the-counter antifungal creams (terbinafine, clotrimazole) work for most skin ringworm in 2 to 4 weeks, and you keep applying for the full course even after it looks gone. Scalp ringworm and nail ringworm need prescription oral medication. School and sports: kids can usually return after treatment has started, per school policy, with the rash covered; wrestling and contact sports typically require treatment underway and lesions covered or cleared.