1 Department of Pediatrics, Division of Allergy and Immunology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; Institute for Immunology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania.
2 Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
3 Departments of Dermatology and Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois.
4 Department of Pediatrics, Division of Allergy and Immunology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; Institute for Immunology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: spergel@email.chop.edu.