Acute onset of illness (minutes to several hours) with involvement of the skin, mucosal tissue, or both (eg, generalized hives, pruritus or flushing, swollen lips, tongue, or uvula) and at least one of the following:

• Respiratory compromise (eg, dyspnea, wheeze or bronchospasm, stridor, reduced peak expiratory flow, hypoxemia)

• Reduced blood pressure or associated symptoms of end-organ dysfunction (eg, hypotonia [collapse], syncope, incontinence)

Two or more of the following that occur rapidly after exposure to a likely allergen for that patient (minutes to several hours):

• Involvement of the skin or mucosal tissue (eg, generalized hives, itch or flush, swollen lips, tongue, or uvula)

• Respiratory compromise (eg, dyspnea, wheeze or bronchospasm, stridor, reduced peak expiratory flow, hypoxemia)

• Reduced blood pressure or associated symptoms (eg, hypotonia [collapse], syncope, incontinence)

• Persistent gastrointestinal tract symptoms (eg, crampy abdominal pain, vomiting)

Reduced blood pressure after exposure to known allergen for that patient (minutes to several hours):

• Infants and children: low systolic blood pressure (age specific) or >30% decrease in systolic blood pressure

• Adults: systolic blood pressure <90 mm Hg or >30% decrease from that person’s baseline