Apreviously healthy 47-year-old woman presents with an ascending, nonpruritic rash of 3 days’ duration on her legs. She reports that the rash began on her ankles following a day of gardening. She does not recall any recent insect bites and denies chest pain, dyspnea, abdominal pain, fever, arthralgia, arthritis, cough, and hemoptysis. She has never had a similar rash before. The patient’s only medication is an oral antihistamine for seasonal allergies. She has no known drug allergies.