Maybe have you previously had a common cold virus? Conceivably did you recover from the virus? Certainly you survived it! You can't cure a common cold directly, yet your immune system normally creates resistance to any type of cold virus within a couple of days. That is called treated by your own immune system!

Parents have previously had a lot of the rhinitis viruses. Adults have developed immunity to the viruses they have actually suffered from. So there are not quite as many cold viruses around for grownups to become infected with. That is why grownups just get a few runny noses each year whereas children acquire a dozen runny noses each year.
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