Peradventure have you a while ago had acute rhinitis? By any chance did you eliminate the cold? Of course you survived it! You will not heal a common cold itself, yet your body generally creates resistance to a particular cold infection within several days. We call that cured by your own immune response!

Adults have already had a great deal of the rhinitis viruses. Grownups have developed resistance to the ones they have suffered from. So there are not as many cold viruses remaining for grownups to acquire. That is why grownups only get a couple of runny noses per year whereas kids succumb to 10-12 colds per year.
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