Abstract: Am J Physiol Lung Cell Mol Physiol 320: L750–L756, 2021. First published February 9, 2021; doi:10.1152/ajplung.00552.2020 RAPID REPORT Carrageenan-containing over-the-counter nasal and oral sprays inhibit SARS-CoV-2 infection of airway epithelial cultures € tz,1* Carina Conzelmann,1* Giorgio Fois,2 Ru € diger Groß,1 Tatjana Weil,1 Lukas Wettstein,1 Desiree Schu 3 4 € ller,1 and Steffen Stenger, Alexander Zelikin, Thomas K. Hoffmann,5 Manfred Frick,2 Janis A. Mu 1 € nch Jan Mu 1 Institute of Molecular Virology, Ulm University Medical Center, Ulm, Germany; 2Institute of General Physiology, Ulm University, Ulm, Germany; 3Institute for Microbiology and Hygiene, Ulm University Medical Center, Ulm, Germany; 4 Department of Chemistry and iNano Interdisciplinary Nanoscience Centre, Aarhus University, Aarhus, Denmark; and 5 Department of Otorhinolaryngology, Head and Neck Surgery, Ulm University, Ulm, Germany Abstract Pharmaceutical interventions are urgently needed to prevent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and transmission. As SARS-CoV-2 infects and spreads via the nasopharyngeal airways, we analyzed the antiviral effect of selected nasal and oral sprays on virus infection in vitro. Two nose sprays showed virucidal activity but were cytotoxic precluding further analysis in cell culture. One nasal and one mouth spray suppressed SARS-CoV-2 infection of TMPRSS2-expressing Vero E6 cells and primary differentiated human airway epithelial cultures. The antiviral activity in both sprays could be attributed to polyanionic i- and κ-carrageenans. Thus, application of carrageenan-containing nasal and mouth sprays may reduce the risk of acquiring SARS-CoV-2 infection and may limit viral spread, warranting further clinical evaluation. carrageenan; sulfated polysaccharides; virucidal; virus inhibition; virus transmission