From: World Allergy Organization Guidelines for the Assessment and Management of Anaphylaxis
Anaphylaxis is highly likely when any one of the following three criteria is fulfilled |
1. Acute onset of an illness (minutes to several hours) with involvement of the skin, mucosal tissue, or both (eg, generalized urticaria, itching or flushing, swollen lips-tongue-uvula) |
   AND AT LEAST ONE OF THE FOLLOWING: |
   A) Respiratory compromise (eg, dyspnea, wheeze-bronchospasm, stridor, reduced PEF, hypoxemia) |
   B) Reduced blood pressure or associated symptoms of end-organ dysfunction (eg. hypotonia [collapse], syncope, incontinence) OR |
2. Two or more of the following that occur rapidly after exposure to a likely allergena for that patient (minutes to several hours) |
   A) Involvement of the skin-mucosal tissue (eg, generalized urticaria, itch-flush, swollen lips-tongue-uvula) |
   B) Respiratory compromise (eg, dyspnea, wheeze-bronchospasm, stridor, reduced PEF, hypoxemia) |
   C) Reduced blood pressure or associated symptoms (eg, hypotonia [collapse], syncope, incontinence) |
   D) Persistent gastrointestinal symptoms (eg, crampy abdominal pain, vomiting) OR |
3. Reduced blood pressure after exposure to known allergenb for that patient (minutes to several hours) |
   A) Infants and children: low systolic blood pressure (age-specific) or greater than 30% decrease in systolic blood pressurec |
   B) Adults: systolic blood pressure of less than 90 mm Hg or greater than 30% decrease from that person's baseline |