Despite the name, ringworm has nothing to do with worms. It's an infection that leaves round, scaly, red rashes and patches of hair loss on the scalp. Ringworm is most common in children between the ages of 3 and 7, but it can affect adults, too. It’s spread through close contact or by sharing hats, clothing, towels, and combs. In rare cases, it's possible to catch ringworm from a dog or cat.