I am not medical professional, but I don't worry too much about using makeup after being sick. I don't wear any while I'm ill (I not going anywhere, after all). Even though I may have used makeup while infected before I experienced symptoms, after recovering, I would have the antibodies in my system to fight that particular disease, so I shouldn't get sick again (not the case with cold sores, in that case throwing away lip products keeps you from getting more). This may not work out for people with immune issues (again, not a medical professional), but I haven't had a problem doing this. Last month, I was hospitalized for pneumonia and also had covid, but I've remained healthy after returning to using makeup.