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A 10-year old child is brought in for swelling that developed 2 hours ago around the mouth as well as a sensation of difficulty swallowing and breathing. Vital signs are normal and she is not hypoxic nor stridorous, but she does have right sided perioral swelling as well as mucous membrane swelling. There is no discoloration. She has no urticaria, pruritis, nor hypotension. She had dental work on her right lower teeth the day prior, and had local anesthetic injection for that. She took one dose of acetaminophen the day prior and one dose 6 hours ago. Her stepfather gave her diphenhydramine 1 hour ago, but it hasn’t helped. The child denies trauma and says that she felt tingling in the area for 1 hour prior to the onset of swelling.

Which is the most likely cause of this patient’s swelling?