It usually follows a painful intervention such as an injection and is manifested by pallor, light-headedness, nausea, profuse diaphoresis, and syncope. Symptoms improve promptly with recumbency and disappear altogether without treatment in 20 to 30 minutes. The lack of pruritus in the presence of a slow pulse rate and normal blood pressure distinguishes a vasovagal attack from anaphylaxis. Fictitious allergic reactions Ingestion of spoiled fish from the tuna family may result in urticaria, pruritus, flushing, gastrointestinal upset, and headache. Other factors, such as the presence of a carcinoid tumor or a reaction between alcohol and chlorpropamide, can cause flushing-type reactions.
Psychosomatic conditions can present as vocal cord dysfunction or outright fictitious anaphylaxis.
The measurement of mast cell tryptase in the blood confirms the diagnosis of anaphylaxis. The immediate goal is to maintain an adequate airway and support the blood pressure. Patients having severe reactions should be given oxygen. Epinephrine should be administered as soon as the diagnosis is made. For this reason, intravenous epinephrine is given slowly in low doses.