CD63 and Airway obstruction: A recent ED study showed only a minor increase in CD63 expression on circulating basophils during anaphylaxis, and only one of 31 predominantly venom‐allergic patients had >15% CD63‐activated basophils, despite the fact that the majority experienced a severe anaphylactic reaction with bronchospasm, airway obstruction, hypoxaemia or hypotension, or collapse.50