Table 1. Symptoms and differential diagnoses in patients with suspected histamine intolerance.

Symptoms	Differential diagnosis/diagnoses
Flush*	Neuroendocrine tumors; mastocytosis
Itching*	Urticaria, pruritus sine materia, prurigo
Nausea/vomiting*	Ventricular ulcer, duodenal ulcer
Diarrhea and abdominal pain*	Chronic inflammatory bowel diseases, carbohydrate utilization disorders (lactose intolerance, fructose malabsorption), celiac disease, matocytosis
Rhinitis*	Allergic and non-allergic rhinitis
Dyspnea, voice disorder*	Allergic and non-allergic asthma
Drop in blood pressure, dizziness, tachycardia*	Anaphylaxis, mastocytosis

*The analysis of symptoms in terms of temporal occurrence gives important differential diagnostic indications; only if there is a temporal association with food intake (minutes to 4 hours) is there a suspicion of food intolerances.