Chronic @entity110 is frequent. Apart from physical and @entity56 , a cause is infrequently identified. A lot of causes are suspected but frequently not well documented. As a consequence, very different diagnostic recommendations are proposed to the clinician. We have performed an extensive review of the literature, in order to determine the quality of evidence for each suspected etiology. The search has been performed in the following data base Embase, Pascal, Cochrane Library and Medline, on a ten years period. It has been completed with data from the selected articles. @entity166 , @entity1374 , @entity262 and @entity5 have been reviewed. When possible, only comparative articles have been included (case-control studies mainly). When not, articles with poor methodology have been included. For each article, methodology and results are reported.

[Which investigations should be performed in chronic XXXX ?].

@entity5 :: ('MESH:D009369', 'Disease') :: ['cancer'] @entity262 :: ('MESH:D034721', 'Disease') :: ['systemic diseases'] @entity56 :: ('MESH:D004342', 'Disease') :: ['allergic urticaria'] @entity166 :: ('MESH:D003141', 'Disease') :: ['Infectious diseases'] @entity110 :: ('MESH:D014581', 'Disease') :: ['urticaria'] @entity1374 :: ('MESH:D013959', 'Disease') :: ['thyroid diseases']
@entity110 :: (MESH:D014581,Disease) :: ['urticaria']
