When you see this word, you may picture a curled-up worm. But ringworm isn't an
animal — it's a contagious infection on the skin, scalp, or nails that's caused
by a type of germ called a
fungus. It's called ringworm because of how the rash looks
— it's shaped like a ring that is red and swollen on the edge and healthy-looking
in the center. Ringworm affects people of all ages, but is especially common in kids.