Microcrystalline Quercetin and Seasonal Histamine-Response Biology: Mast-Cell Findings Integrated with Human Pollinosis Evidence

The NVTIA® microcrystalline quercetin ingredient was examined at two levels: physicochemical quality and mast-cell mediator response. The optimized batch contained 91.6% quercetin, 1.9% residual quercetin glycosides and 94.8% total flavonols, with residual ethanol of 218 ppm, D50 of 9.6 μm and D90 of 28.4 μm. In RBL-2H3 cells stimulated with calcium ionophore A23187, the model-group histamine-release level was set to 100%. Ordinary coarse quercetin at 20 μg/mL yielded 82.7%, whereas the optimized material produced 81.4%, 67.5% and 55.8% at 10, 20 and 40 μg/mL; cell viability at these concentrations was 97.2%, 96.1% and 93.5%. Two additional microcrystalline batches gave 71.8% and 65.9% histamine release at 20 μg/mL. Human pollinosis trials have reported changes in selected nasal or ocular symptoms after quercetin-related flavonol interventions, while a 2025 meta-analysis of polyphenolic interventions found improvement in several seasonal allergic-rhinitis symptom domains. The experimental data therefore identify a concentration-dependent mast-cell response for a defined, highly dispersible quercetin material. A formulation-specific human study can extend this work by measuring quercetin exposure, histamine-related mediators and validated seasonal symptom outcomes in the same protocol.