Struß N, et al. - Given that Nascum-Plus (NP), a commercially available thixotropic gel, was designed to reduce dryness and soreness of the nasal mucosa and prevent the absorption of small particles, researchers conducted this open-label, cross-over, sequence-randomized, monocentric trial to evaluate the effectiveness of single-dose NP in treating nasal symptoms and secretion during challenge in an allergen challenge chamber (ACC). The impact of this treatment on biomarkers and immune cells of the allergic cascade were also measured. This trial randomized 18 adults with SAR and a positive skin prick test reaction to Dactylis glomerata pollen to receive NP or no treatment during two 4-h ACC sessions 3 weeks apart. NP significantly decreased nasal symptoms, evaluated by total nasal symptom score, and minimized nasal secretion, while the nasal fluid had no significant impact on biomarkers and immune cells. For patients with allergic rhinitis, the physical barrier built by NP nasal gel can be applied safely. This decreases allergic nasal symptoms and secretion but it does not affect local inflammatory biomarkers by administering one dose.