What's the contagious period for a cold from one person to another?
First, scientists involved with common cold research do not know exactly how long a person with a cold is contagious. Based on previous studies, their best guess is that a person becomes contagious about two to three days before developing the usual symptoms of a cold.Second, this contagious period can last until the person no longer shows any symptoms.So in theory, a person is contagious for about two weeks. (Click Cold Symptoms to read about the symptoms of the common cold or Cold and Flu Symptoms to learn the difference between a cold and the flu.).Let's assume you're the one with the cold.During the two-week period when you're contagious, research indicates that you'll be most likely to transmit the cold virus when you're experiencing cold symptoms. The period when you're most contagious is when your symptoms are at their worst -- day 2 to day 4 of the cold.et's assume you're the one with the cold. During the two-week period when you're contagious, research indicates that you'll be most likely to transmit the cold virus when you're experiencing cold symptoms. The period when you're most contagious is when your symptoms are at their worst -- day 2 to day 4 of the cold.