A 16-year-old boy presented to the clinic with symptoms of strep throat including a sore throat for 3 days. On examination, he exhibited signs of strep throat including tonsil swelling and exudate. A rapid strep test was positive, confirming strep throat. He was prescribed penicillin but had an anaphylactic reaction. This type of severe allergic reaction is caused by IgE antibodies produced in response to environmental allergens like penicillin, which is a fungus. While he had no known drug allergies, he likely had a previous sensitization to penicillin that caused the anaphylactic reaction upon administration.