A 46-year-old woman presented to the emergency department with an 8-hour history of progressive throat pain, dysphagia, and odynophagia. Of note, she had begun her day by taking a magnesium oxide supplement for the first time. She reported no fever, chills, shortness of breath, trauma, or recent upper respiratory tract infection. Her medical history was significant for asthma, hypertension, and mitral valve prolapse. She also recalled an episode of acute tongue swelling during childhood.