Erythema migrans is a skin condition characterized by a distinctive rash that often appears as a red, circular patch with a lighter center. It is commonly associated with Lyme disease, which is caused by the bacterium Borrelia burgdorferi and transmitted through the bite of infected ticks. The rash typically develops within a few days to weeks after the bite and can expand over time. The appearance of erythema migrans is often described as a "bull's-eye" pattern, but it can vary in shape and size. While the rash itself is not usually painful, it may be accompanied by other symptoms such as fever, fatigue, and joint pain. Early diagnosis and treatment are important to prevent complications associated with Lyme disease.