Chronic rhinosinusitis is a highly prevalent disease resulting in high economic burden. Effective therapeutic options are needed. Rhinosinusitis-related biofilms are a likely contributor to recalcitrant disease. Emerging evidence shows that colloidal silver nanoparticles may be effective for reducing biofilms. The investigators intend to perform a randomized, double-blinded, placebo-controlled clinical trial to evaluate the effectiveness and safety of intranasal colloidal silver nanoparticles in adult patients with chronic rhinosinusitis. The investigators hypothesize that compared to placebo, treatment with intranasal colloidal silver for chronic rhinosinusitis will lead to a significant improvement in symptom scores and will not be associated with increased rate of adverse effects.