RESUMEN
INTRODUCTION: The relationship between Blastocystis spp. and chronic spontaneous urticaria (CSU) is unclear. The aim of this study was to evaluate the role of this parasitic infection on CSU and to search for risky groups in CSU patients with this parasite. METHODS: Seventy adult CSU patients with Blastocystis spp. in their stool samples forming Group A and 70 CSU patients without any parasite as Group B were prospectively compared regarding urticaria activity score-7 (UAS7), medication scores (MS), and laboratory parameters. All patients received CSU treatment, and additionally, those in group A received an antiparasitic antibiotic. Eight months later, the same parameters were compared between the ones in remission (group A1) and those still having CSU symptoms (group A2) in group A. RESULTS: UAS7 and MS were lower in group A than in group B (p: 0.007, p < 0.001) 8 months later, while the initial scores were similar. The presence of food hypersensitivity reactions (FHRs) was higher in group A than in group B (p < 0.001) and was detected as a significant risk factor in the presence of Blastocystis spp. infection (p: 0.002, OR [CI] = 0.151 [0.045-0.502]). In group A, UAS7, MS, serum total IgE levels, and blood eosinophil counts decreased 8 months later (p < 0.001, p < 0.001, p: 0.003, p: 0.004, respectively). Additionally, total IgE levels and eosinophil counts decreased in group A1 (p: 0.033, p: 0.002) while they did not change in group A2. DISCUSSION/CONCLUSION: The eradication of Blastocystis spp. can improve the disease activity in CSU and the presence of FHRs seems to be risky in CSU patients with Blastocystis spp.