Two of my sons had colds a couple of weeks ago. They seemed to get over them, just in time for my other two kids to get it. My youngest however seems better and then will end up coughing again or having the runny nose. It seems to go away for a few days, but not enough sleep, not eating enough (he does not like to eat) or playing outside when it's cold seems to bring it right back. How can I get rid of it and keep it away?