What disease is characterized by circular scaly areas where hair has been lost?

Ringworm is a fungal infection that manifests as circular, scaly patches of hair loss on the skin. It is caused by dermatophytes, a type of fungus that infects the outer layer of skin, leading to inflammation and the characteristic symptoms. The edges of the circular lesions are often more inflamed or raised compared to the center, creating a distinctive appearance that makes it recognizable.

In contrast, fleas are external parasites that cause itching and irritation but typically do not cause circular patches of hair loss. Dermatitis is a broad term for inflammation of the skin that can result from various causes, including allergies or irritants, and does not specifically present with the circular lesions that define ringworm. Scabies is caused by a mite infestation, leading to intense itching and a rash, but it does not typically result in the same circular hair loss patterns. Thus, ringworm distinctly aligns with the description provided in the question.