Anaphylaxis Diagnosis and Treatment

Diagnostic Criteria

The NIAID/FAAN consensus establishes that anaphylaxis is diagnosed when any one of three clinical criteria is fulfilled, as validated in emergency department settings 1, 2, 3, 4
Criterion 1 includes acute onset of skin/mucosal involvement plus at least one of the following: respiratory compromise, reduced blood pressure or end-organ dysfunction 1, 2, 3, 5
Reduced blood pressure or end-organ dysfunction is a key component of Criterion 1, as established by the Journal of Allergy and Clinical Immunology 3
The American Academy of Pediatrics recommends that skin findings are absent in 10-20% of anaphylaxis cases, so diagnosis and treatment should not wait for cutaneous manifestations 1, 2

The American Heart Association recommends intramuscular epinephrine administered into the anterolateral thigh as the first-line, life-saving treatment for anaphylaxis, which must be given immediately 1, 2, 6
The dose for adults and children ≥30 kg is 0.3 to 0.5 mg (0.3 to 0.5 mL of 1 mg/mL solution) intramuscularly, to be repeated every 5-10 minutes as necessary, as per the American Academy of Pediatrics 1, 2
Intramuscular injection in the vastus lateralis achieves peak plasma concentrations in 8±2 minutes, compared to 34±14 minutes with subcutaneous deltoid injection, according to the Pediatrics journal 1
The American College of Allergy, Asthma, and Immunology states that epinephrine is a direct-acting sympathomimetic agent that increases vasoconstriction, reverses hypotension, decreases mucosal edema, increases cardiac inotropy and chronotropy, produces bronchodilation, and downregulates further mast cell mediator release 1, 2

The Gell and Coombs Classification includes four types of hypersensitivity reactions, with Type I being IgE antibody-mediated (immediate hypersensitivity), as described in the Annals of Oncology 5
Type I hypersensitivity reactions include anaphylaxis, allergic rhinitis, food allergies, insect sting reactions, urticaria, and allergic asthma, according to the Annals of Oncology 5
Anaphylaxis is exclusively a Type I hypersensitivity reaction, though the term "anaphylactoid" has been used historically for clinically identical reactions triggered by non-IgE mechanisms, as noted in the Annals of Oncology 5