Changes

==Pathogenesis==

==Pathogenesis==

The aetiopathogenesis of urticaria is complex and many causes have been suggested. The basic pathogenesis is thought to be due to degranulation of mast cells and basophils leading to the release of inflammatory mediators and an increase in vascular permeability. This may be due to exogenous or endogenous hypersensitivity reactions. Exogenous urticaria may occur as a result of exposure to chemicals, medication and insect bites or stings, shampoos or insecticides. Endogenous urticaria occurs following inhalation of allergens such as pollens.  

The aetiopathogenesis of urticaria is complex and many causes have been suggested. The basic pathogenesis is thought to be due to degranulation of mast cells and basophils leading to the release of inflammatory mediators and an increase in vascular permeability. This may be due to either an exogenous or endogenous hypersensitivity reaction. Exogenous urticaria may occur as a result of exposure to chemicals, medication and insect bites or stings, shampoos or insecticides. Endogenous urticaria occurs following inhalation of allergens such as pollens.  

==Signalment==

==Signalment==