The age-old dictat about cold weather-that cold weather causes common cold-is certainly a dampner for me, coz I like to drive my bike in the cold winter mornings, with the frosty wind blowing onto my face. But is this just another of those "myths" perpetrated by our ancestors (with "our" I mean mankind's...coz all round the world sneezing children cant venture out into the cold due to overzealous mothers!) ?
With a lot of spare time in my hands, I decided to dig more into this issue...

First thing, yes, there is a Yokozuna-like strong correlation, as you can see in the graph alongside. But does a strong correlation imply cause? That is what the debate is all over in the scientific community.

For long, the scientific opinion has been that cold weather does not cause common cold. there have been controlled experiments performed to that effect, which have repeatedly proved the absence of any cause-effect relationship. Someone has also done experiments in Antarctica and the Arctic, and they found that isolated people in these cold regions do not catch cold!

The rationale put forth for the correlation is that in winter people tend to remain indoors and huddle together, which automatically increases the interpersonal contact, thus leading to a higher chance of the coronaviruses and the rotaviruses spreading. Even the CDC and the NIH are of this opinion and state that the other opinion is just a myth. So that is the official, government stand...Read this 1928 report in American Journal of Public Health, titled The Weather and Common Cold

But still, there are skeptics (like me). I mean, there is such a strong correlation that the prevalent scientific logic seems a convoluted, contrived one. Again, in today's society, what is the difference between crowding in summer and in winter? We remain indoors for most of the time, and still cold continues to raise its ugly head everytime you breathe cold air for a long time, or keep your head wet and so on. So could there be any relationship at all?

Some studies do speak from the other angle. There is one from Cardiff, where 90 volunteers were asked to keep their feet in cold water for a week for 20 mins every day while 90 were control subjects. The investigators observed (symptomatically, though) that 13/90 of the test and 5/90 of the control suffered from common cold (I dont have the p-values)...which means more than twice the control group had cold.

Another study does some unique experiments in horses!!!! The researchers were trying to find out the reason behind exercise-related asthma. They found that inhalation of cold weather causes IL-4 increase in the nasal passage. IL-4 is a cytokine that triggers allergic reactions.

Other logic suggests that the nasal mucosa gets dry due to cold weather (Yah! I know that! My nose-digging frequency shoots up in the cold season!), which may allow an easy access to the virus. Or that the cold conditions activate the latent virus and causes relapse of the infection. (Although there isnt much evidence on the last point).

According to me, there is some logic in this line of thinking, that cold would act as an irritant and facilitate a viral infection. Because the "indoor-crowding" theory is just too absurd.

On the other hand, there is one good outcome of my research. I learnt that Chicken Soup (also some For The Soul, by the bedside) is very good for common cold, and it is not just a hocus-pocus advice. A study published in Lancet goes by the title - Hot chicken soup for asthma while another one in Chest talks of Effects of drinking hot water, cold water, and chicken soup on nasal mucus velocity and nasal airflow resistance. One more study also shows that Chicken soup inhibits neutrophil chemotaxis in vitro Note that the last research has been criticized in the later comments.

My belief in the effect of cold still remains "not phenomenally dented". Not that I dont believe the research, but the explanation for the observation is not good enough...