It is a bit confusing. I thought the whole point of Mucinex was to help loosen the mucus you have so it can be expelled more easily? But if it reduces some mucus production that would support some saying it can have a drying effect? One thing I came across recently was that guaifenesin is a mild immune suppressant. I know sometimes when I take Mucinex I will feel better than usual that day. Other times no help at all. Maybe worse the next day?