Ringworm is an infection on the skin, hair, or nails caused by a fungus. It is not caused by a worm. The infection usually causes a rash made up of circular patches with raised, red edges. The edges may be peeling or scaly or have bumps that look like blisters. The rash spreads from the edges, often leaving the centre clear. This gives the rash a ring shape.

The medical term for many fungal infections is tinea, followed by a word that describes the location of infection. For example, tinea faciei is ringworm of the face.

Ringworm of the scalp or beard usually requires treatment with antifungal pills to completely destroy the fungi. Other kinds of ringworm often can be treated at home with medicines available without a prescription, such as antifungal creams, powders, and pills. But if the rash is widespread and severe, prescription antifungal pills may be needed.