Every day, you inhale countless potentially infectious particles. If one gets past the mucus lining in your upper airway and enters the lungs, you could get sick. When you exhale respiratory particles, others are also put at risk. For more than a decade, Harvard aerosols expert David Edwards has been working on what he calls the nasal “equivalent to washing your hands” to reduce these risks. He thinks he’s found it in FEND ($60), a drug-free salt- and calcium-based nasal mist that strengthens the mucus lining, helping it trap and flush out tiny pathogens. In a preliminary study, people who used FEND exhaled about 75% fewer aerosol particles than those who didn’t, suggesting it could be a worthy addition to the disease-prevention arsenal, along with handwashing, masking and social distancing. —Jamie Ducharme