TLR4 and urticaria: In the context of urticaria, LPS may facilitate mast cell degranulation via Toll‐like receptor 4 (TLR4) resulting in the release of pro‐inflammatory cytokines, while SCFAs may inhibit both IgE‐mediated and non‐IgE‐mediated mast cell activation via anti‐inflammatory Il‐10 and PGE2.26