Unveiling the role of neutrophils in chronic spontaneous urticaria: Beyond mast cells.

Mast cells and eosinophils are considered pivotal contributors to the pathogenesis of chronic spontaneous urticaria (CSU). However, emerging evidence suggests that neutrophils also play a central role. Cutaneous mast cells and macrophages orchestrate the recruitment of neutrophils through the regulation and activation of diverse processes, including heightened local vascular permeability and chemokine release. Studies have demonstrated increased activation and elevated levels of neutrophil-related cytokines in CSU patients. Moreover, neutrophils have been proposed as antigen-presenting cells during the late-phase reaction of immunoglobulin E-mediated allergy and have been associated with the expression of calcitonin gene-related protein and vascular endothelial growth factor in CSU. Histopathological analysis of lesional skin in CSU patients revealed significantly higher eosinophil and neutrophil counts than unaffected skin. However, the extent of neutrophil infiltration in the skin does not appear to correlate with the number of neutrophils in peripheral blood. The utility of the neutrophil-lymphocyte ratio as a marker for disease activity or remission in CSU remains inconclusive. Neutrophil-targeted therapy may confer benefits for CSU patients who exhibit resistance to antihistamines. Omalizumab has demonstrated its ability to reduce neutrophil counts, the neutrophil-lymphocyte ratio, and the neutrophil-monocyte ratio in peripheral blood. While dapsone and colchicine are recommended as alternative treatment options for CSU, their evidential support from published studies remains limited. Inhibitors targeting interleukin-1 and neutrophil-related cytokines have been proposed as potential therapeutic interventions for patients exhibiting neutrophil predominance. Further research is warranted to gain deeper insights into the involvement of neutrophils in CSU and to explore potential therapeutic interventions.