Cold and colds

Growing up in Sri Lanka, it was an article of faith with my mother (and the mothers of many of my friends) that after a shower, we should not go outside while our hair was still wet because that increased the risk of us catching a cold or getting a chill. If we happened to get caught in the rain, we were told to quickly dry ourselves thoroughly so that we did not catch a cold. But Sri Lanka is a tropical country where what is considered ‘cold’ would be like a balmy summer day in the US. Furthermore houses have very open architecture with open windows and doors so that air is freely circulating and hence there is little difference between ‘inside’ and ‘outside’ except that inside one had a roof over one’s head. Hence these restrictions made no sense. But given the power of confirmation bias, it was always easy to find such a cause to blame whenever one caught a cold.

In the US, children are told to dress warmly when going out in cold weather so that they too will not catch a cold. So does wet hair or ambient cold increase the chances of catching cold? This article looks at the relationship between being cold and wet and catching a cold and, as with so many things, it is a little complicated.

Many of us have heard: “Don’t go outside without a coat; you’ll catch a cold.”

That’s not exactly true. As with many things, the reality is more complicated. Here’s the distinction: Being cold isn’t why you get a cold. But it is true that cold weather makes it easier to get the cold or flu. It is still too early to tell how weather impacts the COVID-19 virus, but scientists are starting to think it behaves differently than cold and flu viruses.

Many viruses, including rhinovirus – the usual culprit in the common cold – and influenza, remain infectious longer and replicate faster in colder temperatures. That’s why these viruses spread more easily in winter. Wearing a heavy coat won’t necessarily make a difference.

More specifically, cold weather can change the outer membrane of the influenza virus; it makes the membrane more solid and rubbery. Scientists believe that the rubbery coating makes person-to-person transmission of the virus easier.

It’s not just cold winter air that causes a problem. Air that is dry in addition to cold has been linked to flu outbreaks. A National Institutes of Health study suggests that dry winter air further helps the influenza virus to remain infectious longer.

In addition, cold weather dries out your eyes and the mucous membranes in your nose and throat. Because viruses that cause colds and flu are typically inhaled, the virus can attach more easily to these impaired, dried-out passages.

So there is a bit of truth in the idea that ambient cold can lead to one being more likely to catch a cold but that is not due to the individual being cold but what happens with the virus in cold temperatures.

I suspect that these beliefs arose because of the external conditions that do exist in the temperate climates then got transmitted all over the world and even to the tropics where those conditions do not apply.


  1. Pierce R. Butler says

    I find that a sudden change of temperature will often induce sneezing (in itself often considered a cold symptom) -- further feed for confirmation bias.

  2. Bob Gotsch says

    In Calcutta and Sri Lanka that might be a perceived risk. I remember in those famous Indian films from 40 or so years ago a child in Calcutta got wet in the rain and may have died. I was somewhat stunned by that fact because I had been in India and that seemed so implausible. Now you mention a similar caution in Sri Lanka, which reminded me of that film after all these years, and which also seems implausible because I have also been in Sri Lanka. We just didn’t think that way in mid-USA, so rather than being a world-wide belief, I suspect might be an Indian and Sri Lankan idea. Anyway, thanks for the memory.

  3. Mano Singham says

    Bob @#2,

    That film you mention was, I think, Satyajit Ray’s famous film Pather Panchali. You may be right that this is a myth that is more prevalent in the subcontinent but the fact that the article I linked to was by someone based in the US, suggests that it must be somewhat common here too.

  4. machintelligence says

    In my mother’s case it wasn’t cold so much as being in a draft. Moving air is apparently dangerous.
    When I told her I would run a ceiling fan at night rather than air conditioning, it worried her.

  5. Ridana says

    I got the wet-hair lecture from my Ohio mom too.
    It’s a running joke that whenever anime characters get rained on or otherwise get caught in wet clothes, they will invariably come down with a life-threatening cold within 12 hours. This can sometimes be averted by shedding said wet clothes, but not always. But one must act quickly or it’s hopeless!
    I always wondered about the prevalence of this trope and its origins. While it’s obviously used as a lazy contrivance for drama or sexual shenanigans, it must come from somewhere. Infectious diseases and homelessness were pretty rampant in post-war Japan, so I’ve wondered if that had something to do with it. But there is also the folk belief in Japan that if you sleep with your stomach bare, you will catch cold or worse, and belly-warmers (haramaki) to guard against this, once a symbol of old men and gangsters, are now a fashion statement. In any case, people seem to wear them to keep warm across the country, from nearly sub-arctic Hokkaido to sub-tropical Okinawa.

  6. Heidi Nemeth says

    Having just taken a shower, my sister-in-law’s sister invoked what she knew to be the Chinese belief that going outside with wet hair would cause her to catch cold so she, my sister-in-law, and my father (all Caucasians) were allowed to stay at a Chinese-only hotel in China from which they were about to be expelled. The belief that colds are contracted by being wet and cold seems universal. I read in Guns, Germs and Steel that starvation doesn’t usually kill people, rather disease kills of those who are starving. It makes sense that people are more susceptible to colds if they are very hungry -- and being cold increases a person’s caloric needs. To catch a cold in today’s model of infection, the virus must invade a susceptible host is sufficient amount to cause disease. Cold and hunger can make a host more susceptible, requiring a smaller amount of invading virus to cause infection.

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