Sometimes antiviral medicines (such as acyclovir) may be added to corticosteroid medicines to treat Bell's palsy. But evidence for using antiviral medicines is weak. They may help in some cases, but in general they do not affect recovery. As most cases of Bell's palsy are probably due to a viral infection, it seems logical that antiviral medicines may help. Some medicines can stop the chickenpox and cold sore virus from multiplying. It is possible that taking a course of steroids plus a course of antiviral medicine may work a little better than taking a course of steroids alone.