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.
http://cold.emedtv.com/common-cold/common-cold-contagious-period.html
'Don’t worry, I’m not contagious' – and other microbiological delusions. As the cold season dribbles relentlessly onward, it’s worth considering who is – or is not – to blame for your misery. Tuesday 22 April 2014 05.00 EDT Last modified on Thursday 1 June 2017 16.12 EDT.
https://www.theguardian.com/science/occams-corner/2014/apr/22/contagious-cold-microbiological-delusion
It is only necessary to see a health care provider if you have any of the following symptoms: Cold lasting more than ten days. Dark green, very thick, or bloody phlegm. A fever of higher than 101.5 ° F for more than three days. A rash. Chest pain, shortness of breath, or wheezing.
http://goaskalice.columbia.edu/answered-questions/when-are-colds-contagious
There are untold numbers of contagious microbe strains on the prowl, each with their own incredibly complex infection processes. Because of the variability of incubation periods and viral shedding windows (which can range for days), the most obvious culprit – your spouse, your child at nursery, the chap who sneezed all over you on the Victoria line – may be a red herring.
https://www.theguardian.com/science/occams-corner/2014/apr/22/contagious-cold-microbiological-delusion
“Don’t worry, I’m no longer contagious,” she told me breezily. Quite understandably, once our symptoms have peaked and we’re feeling a bit better, we may assume that the danger of spreading illness is past. But is it really that simple? It all depends on the particular microbe and strain. Rhinovirus, for example, one of the agents that causes the common cold, loads up your snot with so many particles that you can easily be infectious a full two days after your symptoms hit, and possibly longer.
https://www.theguardian.com/science/occams-corner/2014/apr/22/contagious-cold-microbiological-delusion
Common Cold Contagious Period. 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. The height of the common cold contagious period is when symptoms are at their worst -- usually around day 2 to day 4 of the cold.
http://cold.emedtv.com/common-cold/common-cold-contagious-period.html
The common cold contagious period may begin two to three days before symptoms appear and lasts about two weeks. As explained in this eMedTV article, the peak of the common cold contagious period usually occurs between day 2 and day 4 of the cold.
http://cold.emedtv.com/common-cold/common-cold-contagious-period.html
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.
http://cold.emedtv.com/common-cold/common-cold-contagious-period.html
Common Cold Contagious Period 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.
http://cold.emedtv.com/common-cold/common-cold-contagious-period.html
'Don’t worry, I’m not contagious' – and other microbiological delusions. It’s that strange time of year when, despite springtime breaking out all over town – tulips, apple blossom, sunshine, the works – everyone in the known universe appears to be ill.
https://www.theguardian.com/science/occams-corner/2014/apr/22/contagious-cold-microbiological-delusion
how long is the contagious period for a cold
The peak of the common cold contagious period usually occurs between day 2 and day 4 of the cold.