How long will I be contagious for with a sinus infection or cold?

There is difference. Most people do not transmit sinus infections; most clinicians agree that except for rare instances, sinus infections are not contagious expect in rare cases. A person infected with a cold virus may be contagious for two to three days before any symptoms appear and remain so until he or she doesn't show any symptoms. This is a period of up to two weeks or so.