Cutaneous symptoms (90%)
Hives
Angioedema
Itching
Morbilliform rash
Respiratory symptoms (70%)
Wheezing
Shortness of breath
Throat itching or tightness
Hoarseness
Stridor
Hypoxia, cyanosis
Gastrointestinal symptoms (40%)
Abdominal pain
Nausea, vomiting
Diarrhea
Cardiovascular symptoms (35%)
Hypotension
Chest pain
Palpitations
Central Nervous System
Uneasiness
Altered mental status
Headache, dizziness, confusion
Syncope
Hives
Angioedema
Itching
Morbilliform rash
Wheezing
Shortness of breath
Throat itching or tightness
Hoarseness
Stridor
Hypoxia, cyanosis
Abdominal pain
Nausea, vomiting
Diarrhea
Hypotension
Chest pain
Palpitations
Uneasiness
Altered mental status
Headache, dizziness, confusion
Syncope
Symptoms peak within 30 minutes to 1 hour after onset, resolve within 30 minutes to 1 hour of receiving treatment
Biphasic reactions are rare and can occur anywhere from 10 minutes up to six days after an initial reaction.
Uniphasic response, followed by asymptomatic period of hour or more, then return of symptoms
The second phase does not necessarily resemble the first!
More likely with a severe initial presentation, hypotension, and recurrent epinephrine dosing requirements in the emergency department
Little evidence to support the use of discharge steroids to prevent a biphasic reaction
0.4% of patients with<unk>  had a rebound event while in the ED
Anaphylaxis
Allergic reaction/urticaria
Heat tetany
Laryngospasm
Angioedema
Cold urticaria
Anxiety attack
Flash pulmonary edema