A 28-year-old man presents to clinic with a painless chancre in the glans of his penis. He is diagnosed with early syphilis and you recommend treatment with intramuscular benzathine penicillin. The patient states that he is allergic to penicillin. He describes a single reaction when he was treated for “Strep pharyngitis” as a young child. He does not fully remember the event but recalls having mild abdominal discomfort, nausea and diffuse pruritus. Does not remember having any respiratory problems or rash. His mother is also allergic to penicillin. He is interested in getting the best possible treatment for his current condition, but he is also concerned about the dangers of allergic reactions, and he is very nervous about getting a penicillin shot. He does not recall receiving any antibiotics in the last 10 years.