orRingworm: A fungal infection. Scaly, crusty, or red circular patches 1⁄2 to 2 inches (12 to 50 mm) across. Patches show central hair loss with a red ring at the periphery. Sometimes just broken hairs around the face and ears. May become infected. Highly contagious, including to humans.
Cortisone excess: Symmetrical hair loss over trunk and body, with darkening of the underlying skin. Seen with Cushing’s disease. May also indicate a thyroid problem. Thinning of the skin is also seen with this condition.