Background While there is evidence of an increased incidence of sinusitis in patients with allergic rhinitis, it is unclear whether an allergic process occurs in the sinus tissues per se. Objective The purpose of this study was to determine whether inhaled pollen reaches the sinus mucosa. Methods Tc99m labeled ragweed pollen was inhaled by five non-atopic adults. Imaging studies of the sinuses were performed with a tomographic rotating gamma camera. To determine the sensitivity of the technique, the nose and the maxillary sinuses of cadaver heads were painted with varying amounts of Tc99m and then similarly scanned. Results Scans of the cadaver heads showed clear resolution between the nasal cavity and the maxillary sinus. It was determined that 20 microcuries was the smallest amount of Tc99m that could be resolved to be in the sinuses. Scans of subjects showed intense activity in the nasal cavity but none in the paranasal sinuses despite the delivery of a supraphysiologic dose of Tc99m ragweed pollen. Conclusion Inhaled ragweed pollen does not appear to enter the paranasal sinuses. It is unlikely that an inhaled antigen-IgE antibody reaction occurs in the sinus mucosa.