Assessment of urticaria and angio-oedema

There are many types of urticaria and the principal form of assessment is b y clinical history and examination. Urticarial weal formation involves acut e, reversible vasodilatation and increased vascular permeability. If the pr ocess is deeper the more diffuse swelling is termed angio-oedema. The major types of urticaria include allergic, physical and idiopathic forms. In all ergic urticaria, IgE-mediated degranulation of mast cells results in weals of short duration which typically respond well to antihistamines. Physical urticarias are induced by physical insults including pressure, scratch, col d, etc. The distribution and duration of individual weals may suggest the c ausal factor. Chronic idiopathic urticaria can be very variable, with indiv idual weals lasting between 90 min and 24 hours. Longer-lasting weals are l ess responsive to anti-histamines and clearly involve other mediators. When longlasting weals fade leaving a bruised appearance urticarial vasculitis is present which may only respond to systemic corticosteroids. In a proport ion of individuals with chronic idiopathic urticaria, auto-antibodies are p resent with specificity for the high affinity receptor for IgE or sometimes , for IgE itself. In general laboratory tests for allergic factors or other assessments of general health are completely unhelpful.