Maybe have you ever before been down with a cold? By any chance did you get rid of it? Obviously you got over it! You can't heal an acute rhinitis itself, but your system typically establishes resistance to a specific cold virus within a couple of weeks. We call that being healed by your own immunity!

Adults have in the past had a lot of the cold viruses. Adults have established immunity to the ones they have had. So there are not numerous runny nose viruses around for adults to become infected with. That is why adults just get infected with a few colds per year whereas kids may get 10-12 runny noses each year.
https://www.ranker.com/writer/herianwvqc