The importance of SP as a proinflammatory mediator in human pathology can not be denied. A role for SP in the pathogenesis of urticaria has long been hypothesized.

Literature data regarding the possible role of SP in chronic CSU have been reviewed and summarized by this study based on pertinent articles that were retrieved by a selective literature search in the PubMed database.

Recent studies demonstrated that circulating levels of SP are significantly elevated, in correlation with disease severity, and that SP-positive basophils are upregulated. SP has been shown to trigger degranulation in basophils derived from CSU patients. Moreover, SP can be involved in pseudo allergic reactions and may act as a histamine-releasing factor. Current evidence suggests that the biological activity of SP can be exerted not only through the conventional NK-1 receptor but also through the recently identified Mas-related G protein-coupled receptors. MRGPRX2 can cause mast cell activation and has been found to be upregulated in patients with severe chronic urticaria.

The study concluded through its findings that the findings of literature seem to support the pathogenic involvement of SP in chronic urticaria/CSU.

Reference: https://clinicalmolecularallergy.biomedcentral.com/articles/10.1186/s12948-018-0101-z