In March, I asked on social networks what was the most difficult for people during the COVID-19 pandemic. I got more than 100 answers and found that in many ways people have the same problem: the unknown.

Liquid hand sanitizers-mostly alcohol-based gels-have experienced an explosion in popularity over the last 10 years. If you’ve recently traveled by plane or set foot in a classroom in the US, chances are you’ve seen hand sanitizers in use.