Intestinal permeability in patients with chronic urticaria-angioedema with and without arthralgia. We evaluated the clinical response to oligoallergenic dietary treatment and the intestinal absorption of a protein antigen, cow milk beta-lactoglobulin (BLG) in 24 patients with chronic urticaria/angioedema syndrome 13 of whom also suffered from joint symptoms. Sixteen patients (77% of those with arthralgia) responded to diet (RD) with marked reduction of symptoms; the others did not respond (NR). Ten (all but one RD with arthralgia) had increased permeability to BLG after oral administration of cow milk. Four with high titers of IgG to BLG showed the highest absorption of BLG and the groups with arthralgia showed higher BLG levels than those without arthralgia. In all cases, specific IgE to cow milk was absent. These data suggest that the symptoms of a subgroup of patients with chronic urticaria, and especially patients with joint complaints that subside with diet, are related to excess intestinal permeability. The measurement of gut permeability to food proteins may be useful to define those who may benefit from dietary restriction. 