The primary pathogenic mechanism of Type I hypersensitivity reactions involves histamine-mediated activation of the H1 receptor (H1R) and the subsequent signaling of the phospholipase C β-inositol trisphosphate (PLCβ-IP₃) pathway. The present study evaluates the in vitro efficacy of a novel nutraceutical mixture—Quercetin, Perilla frutescens, Boswellia serrata, Blackcurrant, Parthenium, Helichrysum, Lactobacillus Acidophilus (L. acidophilus) and Bifidobacterium animalis (B. animalis)—in modulating HRH1 gene expression and the activation of the intracellular second messenger inositol trisphosphate (IP₃). Quantitative PCR (qPCR) analysis revealed that the mixture downregulated HRH1 expression by approximately 33% (p < 0.05) compared to the control group. Furthermore, ELISA assays demonstrated that the mixture significantly reduced IP₃ release by 10.30% (p < 0.05 vs. positive control). These results indicate that the nutraceutical mixture exerts its effects by modulating the H1R-PLCβ-IP₃ pathway through the reduction in both H1 receptor gene expression and IP₃ release. These findings suggest a potential mechanism of action involving the modulation of the histamine H1 receptor. Consequently, the mixture emerges as a promising candidate for further investigation into the H1R-IP₃ activation cascade.