EM (Erythema migrans)

Erythema migrans is a skin rash often associated with early Lyme disease, caused by the bite of an infected tick. It typically appears as a red, expanding ring or bull's-eye-shaped lesion at the site of the bite, usually within a few days to weeks. The rash grows gradually, sometimes reaching up to 12 inches in diameter, and may be warm or itchy but generally not painful. While it is a key early sign of Lyme disease, not everyone develops it, so prompt recognition and treatment are important to prevent further health issues.