Flushing and urticarial syndromes presenting as anaphylaxis

Flushing, urticaria, and angioedema are clinical findings that are commonly associated with anaphylaxis. Flushing can be quite dramatic but is less common in anaphylaxis than are urticaria and angioedema, symptoms that are commonly mentioned together as a single symptom,urticaria/angioedema. Differentiation of dry flushing, due to circulating agents acting directly on smooth muscle, from wet flushing, due to neurogenic triggers from the shared autonomic innervation of blood vessels and sweat glands, can be helpful in sorting out causes of flushing. Flushing may be idiopathic, but may also occur in conditions such as carcinoid syndrome (CS), mastocytosis, mast cell activation disorder (MCAD), pheochromocytoma, medullary carcinoma of the thyroid (MCT), icthyotoxicosis, and other conditions with symptoms that overlap those of anaphylaxis. Chronic urticaria can exist as an independent syndrome that does not commonly have anaphylactic features or signs. However, urticaria can also occur as one of the symptoms of an anaphylactic response. Cholinergic urticaria and cold urticaria are the two physical urticarias that are associated with anaphylaxis.