Chronic Urticaria in Children

Abstract

For a wheal to develop, a given antigen has to bind to an antigen-specific IgE present on the surface of a mast cell. As a result, the mast cell degranulates, releasing histamine and vasoactive mediators. These mediators produce vasodilatation, increased blood flow, and vascular permeability. The final result is fluid extravasation and swelling of the superficial dermis that clinically translates as a wheal. Subsequently, an axonal reflex produces the surrounding flare. This reaction is known as the triple response of Lewis. (see Figure 3).