Presentation	Differential diagnosis
Flush syndrome	Autonomic epilepsy Carcinoid Medullary carcinoma of the thyroid Perimenopausal hot flashes Red man syndrome (i.e., adverse reaction to vancomycin)
Hypotension	Cardiogenic shock Hypovolemic shock Septic shock Vasovagal reaction
Miscellaneous	Anxiety, panic attacks Hereditary angioedema Leukemia with excess histamine production Systemic mastocytosis
Postprandial collapse	Airway foreign body Monosodium glutamate ingestion Scombroid fish poisoning Sulfite ingestion
Respiratory distress with wheezing or stridor	Aspiration of a foreign body Asthma and chronic obstructive pulmonary disease exacerbation Vocal cord dysfunction syndrome