ABSTRACT
Urticaria is extremely common and there are few individuals who do not experience it in one form or another during their lifetime. An important characteristic of urticaria is its transience, but very occasionally urticarial lesions stay for days rather than hours and leave a brownish stain. In angioedema, the lesions are deeper and the swelling much more extensive than in urticarial. Angioedema may accompany urticaria or may occur independently. The ultimate cause of urticaria and angioedema is release of histamine from mast cell granules, but a large number of stimuli can do this. Urticarial lesions develop some time after pressure on the skin, for example from belts or other tight clothing, or from the rungs of a ladder. Penicillin hypersensitivity may cause acute urticaria. Sodium benzoate/benzoic acid used in carbonated drinks and preserved bread may precipitate urticaria in some cases.
