Maybe have you a while ago endured a runny nose? By chance did you heal from the virus? Obviously you did! You can't heal a runny nose itself, but your system normally creates immunity to a certain cold infection within a couple of days. We call that being cured by your personal immunity!

Parents have previously had a lot of the rhinitis viruses. Adults have created resistance to the viruses they have actually had. So there are not quite as many runny nose viruses existing for parents to acquire. That is why adults just acquire a few colds per year and kids succumb to 10-12 colds each year.
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