text: when is the common cold contagious and for how long?   7-14 days they say. as far as when it is contagious it is a virus and is spread by sneezing, coughing and not washing hands. it's contagious as soon as you come in contact with the germ.  this doesn't mean that you will get the cold, most people with a healthy immune system can ward off the common cold. however, if your immune system is depleted it will normally take a good hold of ya.  i hope this answers your question.