Conceivably have you a while ago been down with a cold virus? By any chance did you do away with it? Naturally you did! You will not heal an acute rhinitis directly, but your system typically establishes immunity to any type of cold infection within a few days. We call that being cured by your personal immune system!

Adults have in the past had a great deal of the rhinitis infections. Parents have created resistance to the ones they have actually had. So there are not numerous cold viruses around for adults to acquire. That is why adults only succumb to a couple of runny noses per year whereas children may get a dozen colds each year.
https://ameblo.jp/tituspasj796/entry-12667281445.html