sentences:  The reaction usually occurs in three stages, beginning with the appearance of an erythematous area at the site of injury, followed by development of a flare surrounding the site; finally a wheal forms at the site as fluid leaks under the skin from surrounding capillaries.CUS has been categorized as an immediate hypersensitivity reaction with IgE (a type of anti-body) playing a crucial role in its pathogenesis.Investigations dealing with CUS seem to suggest that a percentage of urticarias encompass a contact mechanism.