Perhaps have you heretofore had a cold virus? Peradventure did you recover from the infection? Certainly you got over it! You will not cure a cold directly, but your body usually develops immunity to a certain cold infection within a couple of weeks. That is called cured by your very own immune response!
Grownups have actually in the past had a lot of the rhinitis viruses. Parents have actually acquired immunity to the colds they have suffered from. So there are not lots of cold infections remaining for adults to become infected with. That is why grownups only get a couple of colds annually and youngsters get 10-12 runny noses per year.