it's designed for allergies, the xylitol is supposed to stop allergens from adhering to nasal walls, and in my experience it helped for that
and i feel like given that mechanism it might do for viruses what it does for allergens, and reduce the risk of infection, i know a study is being done on it for prevention but i don't know if the results are out yet, there was a study done on using it for treatment of people with COVID that showed a reduction in symptoms i think