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Abstract
Background Urticaria (hives) is a rash affecting the skin and mucosa, often characterized by appearance wheals, angioedema, and pruritus. Chronic urticaria (CU) is classified by the occurrence of urticaria which exceeded six weeks (almost daily) without specific triggers and identifiable cause. CU is a common disease that has detrimental effects on quality of life. However, its aetiology remains unclear. There is increasing evidence that dysbiosis of the intestinal microbiota is associated with dermatologic conditions. The human gut microbiome has a significant role in the regulation of the immune system, which can be implicated in the development of immune-mediated diseases such as CU. This systematic review aims to investigate the relationship of gut bacteria and the development of CU.
Methods The systematic literature search was executed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Research commenced using MeSH terms relevant to the topic, (‘gut’ OR ‘microbiome’ OR ‘microbiota’ OR ‘microflora’) AND (‘urticaria’ OR ‘hives’) were performed on four databases (PubMed, EMBASE, ProQuest, Scopus; publication date limit to 29 February 2020). Titles and abstracts of all retrieved studies were screened and refined by the inclusion and exclusion criteria. Studies involving gut microbiome and CU were considered for inclusion. Irrelevant articles based on title/abstract level, case reports, conference abstracts and other studies with no experimental intervention (reviews, book, commentaries) were excluded.
Results Three studies were eligible for final qualitative analysis, with a total of 100 participants. Research findings have shown that CU patients have a significant decrease in abundance of Firmicutes (Lactobacillus; Faecalibacterium prausnitzii), Actinobacteria (Bifidobacterium), Bacteroidetes (Bacteroides fragilis, Bacteroides plebeius), whilst an increase in abundance of Proteobacteria. The research suggested that increased abundance of Proteobacteria might enhance the permeability of intestinal mucus inner layer and enable bacterial infiltration, causing inflammation of epithelium and impairment of gut barrier function which leads to the development of inflammatory skin diseases.
Altered gut microbiome is associated with development of chronic urticaria
Conclusions As a summary, this outcome provides a preliminary understanding of microbial composition in CU patients (figure 1). This offers a new avenue of research for potential CU treatment via maintaining gut health.