Vanillic acid, which is well known as a benzoic acid derivative, has been used as a flavouring agent. Currently, we ascertained the therapeutic potential action of vanillic acid on allergic inflammatory reaction in human mast cell line, HMC-1. Treatment with vanillic acid resulted in a significant decrease in levels of thymic stromal lymphopoietin and pro-inflammatory cytokines compared to phorbol 12-myristate 13-acetate and calcium ionophore A23187 (PMACI)-treated HMC-1 cells. In PMACI-stimulated cells, treatment with vanillic acid also dramatically inhibited activities of caspase-1 and nuclear factor-kB (p65). Furthermore, treatment with vanillic acid suppressed phosphorylation of mitogen-activated protein kinases in PMACI-treated HMC-1 cells. Taken together, these findings suggest that vanillic acid has a beneficial effect on allergic inflammatory disorders.