Why Do We Get Colds When It’s Cold?

At some point during your childhood, you were
probably told not to go out in cold weather with wet hair, or without bundling up, because
“you’ll catch a cold.” But we know the common cold is caused by
viruses, not chilly air. So why does this old wives’ tale hang around? It’s probably because colds are more common
in colder weather. But as far as scientists can tell, that’s
not because you feel cold. There are lots of better explanations for
why colder weather increases your odds of getting sick. The connection between temperature and illness
isn’t simple. Even though colds and other respiratory illnesses
are more common in colder months, not all of them spike in the dead of winter, when
it’s coldest. And the most direct studies we’ve done haven’t
found a relationship between feeling cold and catching a cold. For example, in a randomized controlled trial
published in 1958, researchers divided nearly 400 people into rooms that were either 27
degrees, 16 degrees, or -12 degrees Celsius. Then they put virus-infected mucus up some
of their nostrils. But the temperature didn’t make a difference
— in every room, just over a third of the volunteers that received the infected mucus
got sick. One study from 2005 did find that people who
had their feet soaked in freezing cold water reported more cold symptoms in the days afterward
compared to a control group. But it’s hard to tell how much of that was
influenced by subjects thinking they’d be more likely to get a cold. If feeling cold really does make you more
likely to get sick, there are a couple of ideas that might explain it. One hypothesis argues that even though the
cold doesn’t weaken your immune system overall, it might lower the defenses in your respiratory
system, specifically. And in a paper published in 2016 in the journal
Medical Hypotheses, a microbiologist suggested that viruses lie dormant for extended periods
of time in our bodies, then get activated when the temperature drops. But there are lots of problems with those
ideas. And the vast majority of
research shows that simply being cold doesn’t make you more vulnerable to catching colds. Instead, there are other aspects of cold weather
that might increase your chances of getting sick. Like the fact that the air is super dry. Colder weather is associated with lower humidity,
because at lower temperatures, the air can’t hold as much water. When humidity is high, the droplets of virus-infected
grossness we breathe out or sneeze out or cough out of our bodies stay large and drop
to the floor relatively quickly. But in dry air, they break up into smaller
particles and can float around for hours. Plus, the lack of moisture can dry out the
mucus lining in your nose, which might make it easier for viruses to get past that line
of defense. Another potential problem is that some people
don’t get enough sunlight in the winter, making them run low on vitamin D. Since vitamin
D helps power your immune system, lower levels mean lower defenses against viruses. And then there’s the fact that human behavior
changes during colder months. We’re more likely to stay indoors, which
means we’re more frequently touching stuff infected people touched, and breathing in
the remnants of their sneezes. [deep breath] Mmmm… So, researchers are still trying to pin down
all the different ways cold weather may or may not affect how likely you are to catch
a cold. But the best way to avoid catching one isn’t
necessarily by throwing on another layer, or drying your hair before running out the
door. It’s washing your hands with soap, not touching
your face with unwashed hands, and staying away from people you know are infected. Thanks for watching this episode of SciShow! And a special thanks to our patrons on Patreon,
who help us keep the heat running all winter, and contribute by asking questions like this
one. To submit your own questions, you can head
over to patreon.com/scishow. ♪ OUTRO ♪♪

100 thoughts on “Why Do We Get Colds When It’s Cold?

  1. If you have a cold then you feel a lot worse if you are cold, than if you're warm. If I have a cold, especially one that isn't so bad, I'm more likely to still go out and do things if it's nice and warm than if I have to go shovel snow first.

  2. So i have a question too, most of the time when i go outside to cycle i get a runny nose, and it worsens when there is rain, wind and in the colder months of the year ( mostly autumn and winter, but spring is always save either ) note its not just when i have a cold

  3. Your snowflakes in the thumbnail are incorrect. Snowflakes have 6-fold rotation symmetry (i.e. six 'arms') yours have 8-fold rotation symmetry. 🙂 #SnowFake

  4. Its because the Pharmaceutical companies make it so.

    They're the real ones behind the holiday season. They created a time of year where everyone gets together exchanges foreign viruses and bacterial, get sick and have to run out and buy a ton of meds. Then the fat cats line their pockets and vacation all summer long with the money they made in the winter months.

    Boom, science'd


  5. And there is the fact that the immune system works better around a certain temperature… The reason why fever is actually helping the immune system by providing the right temperature for the enzymes to do their job!

    And there is the fact that cold temperatures can cause rhinitis, dry skin and can damage capillaries. A damaged epithelium is more permeable to infectious agents…

    And there is also the fact that we are less active during the winter… The lymphatic system requires some level of physical activity to be optimal.

  6. I do not get the humidity dependency. Maybe the abs. humidity is smaller but the relative is higher in winter in Europe where winter is cold.

  7. I've had 3 colds this year, all during warm weather. The thing about dry air makes sense, since i live in an area that has very low humidity all year round.

  8. wet hair contribue in to headashe sicknesses in your future, having wet hair make your head more conductive so u lower your head temperature alot and that is not good, have nothing with viruses ot geting sick sick , it will get you sick in the future. not sick from virus

  9. The term cold is relative, for example, today in my region it was -19C but when up to -10C everyone said "Hey it's not too bad now" but someplace like Florida from 30C to 21C would freak them out and they'd probably think they will get sick.
    Just a few days ago I saw in The Guardian newspaper it gave tips on how to not get sick and one was to make sure you change out of damp exercise clothes in case you get chilled. Ugh!!!!

  10. Do similar things happen in hot dry places when it is something like 4% humidity and too hot to go outside, thus resulting in a very similar set of factors as listed in the video.

  11. sir are study is paying 150.00 to put virus infected muscous boogers up your nose to see if you catch a cold. no thanks , good luck with that.

  12. Some Asian cultures have an excellent way of helping reduce transmission of airborne illnesses: folks who are ill with colds, flu, or such wear surgical masks to help lessen the chance of spreading their disease. Last week, I knew I was sick with an influenza-like illness (ILI), so when I went to the medical clinic that handles my needs, I showed up with a mask on my face and instant sanitzer for my hands… because the coughing element of the illness was really, really bad, and I didn't want anyone else getting the nasty virus ravaging my lungs and bronchii. (Same illness sent roommate to hospital for 4 days, so I didn't at all mind looking ridiculous, if it would help others avoid the same fate.)

  13. but doesnt cold reduce the bloodflow, sortof the opposite of inflammation where blood flow is increased to a certain area bringing in more blood and white cells etc.
    dunno, just would make sense that when your nose is cold and with that suffers from reduced blood flow, it would be easier for viruses to reproduce before they are killed?

  14. I almost never get sick and when I do get sick it’s in summer and I get SUPER sick (but luckily I didn’t get sick in a year and a half)

  15. What always gets me sick is when I don't wear a scarf and I'm breathing in really cold windy air.
    gurantee sore throat then to the common cold the next morning .

  16. 1. STRESS: Does stress lower your immune system? Then can being painfully cold for an hour, or more, give you stress?
    2.CHILLS: Also what about when someone gets chills, and if someone gets chills that stays with them even after they return to the warm indoors, does that affect the immune system?

  17. My first thought was the some bacteria that we have slows down its metabolism and becomes so slow it can't prevent the pathogens that enters us

  18. I have a cold now, I had a cold in the middle of the summer this year. So far, the summer one appears to have been worse.

  19. I think getting cold has nothing to do with being cold or cold weather. I ride my bike in winters when temperature drops below zero and never get sick or catch a cold. But everytime I have to use public transportation because it is snowing or raining heavily, I get sick in like 3 days to a week. Public transportation is like a petri dish.

  20. Something i noticed while in high school was that people actually got colds more often during the summer than the winter. During the winter they wore warm clothing and then went into warm class rooms. However, during the summer they wore cooler clothing outside where it would be 80's to 90's and went into 60 degree classrooms in that cooler clothing. My hypothesis was that the constant change in temperature may have negatively effected their cold defense.

  21. Seriously, hand washing is important. Over 8 years I made all my own food and was careful about hand hygiene. I hung out with plenty of sick people but wasn't sick once over all 8 years. People are gross. Almost no one washes with soap and they touch everything including snot when they are sick.

  22. I have a thought that colds and flu may be more prevalent during cold months for a couple reasons, one many people eat more calories during winter months and often foods higher in sugar resulting in a slightly weakened immune system for some people. The other thought is that we all might carry viruses that are not active somewhere in our bodies just waiting for the immune system to become less efficient. Poorer diet and reduced sunlight could be impacting immune systems allowing viruses to take hold more easily in winter months. Add that too reduced physical activity for some people as a result of weather and some people exposed to viruses are possibly more likely to get sick.

  23. I wonder about cold weather and pneumonia, especially with the story of William Henry Harrison (longest inauguration of any US president, no coat or hat, and longest inauguration speech and dead in a month).

  24. I'll save you 3 minutes people get colds in winter more because they are more likely to be in close quarters with other infected people

  25. Here’s a question: can you “sweat out” a cold or fever through exercise? My father (a gym teacher) always insists it’s a real way to help get better.

  26. I always thought it was more of a correlation – more cold temperatures mean that more people are likely to share indoor spaces, and the temperatures inside are warmer and in that sweet spot where bacteria and viruses are happy and healthy. More people touch things, touch their mouths, rub their noses, which are running from the cold, etc, then touch more things that more people are touching. It's really a delightful breeding ground for pathogens, don't you think?

  27. It drives me crazy when my parents spend ten minutes in the cold outside and are already complaining about getting sick, that's not how it WORKS. (Meanwhile my father will put the spoon he put in his mouth in the communal dish or fail to cover his mouth and nose when sneezing.)

  28. This is very simple.
    You catch colds in the cold because the temperature difference between the outside air and the air in your sinuses causes condensation. This condensation (perhaps caused by the hypothalamus increasing your internal temperature) begins to drip out of your nose when awake but when sleep drips down the back of your throat and lungs. Over night infection sets.

    One of the best way to prevent SORE THROATS is to elevate your head so a runny nose doesn't drain into your throat and lung but rather out your nose. (lie on your side with head elevated high) I guarantee you avoid throat and lung infections every time and minimize sinus infections. (Remember the worse time for a cold is while you sleep because these fluid pool in the sinues, back of the throat and lungs as you sleep. That's why you feel worse every morning but get better as the day progresses)

  29. Wash your hands with soap… Rarely
    Dont touch your face with unwashed hands… I do that all the time
    Stay away from infected… I dont avoid anyone who sick any more or less than i would if they wernt…

    And i very rarely ever get sick… ssooo

  30. I blame other people for me being sick with a cold for like 2-3 weeks in December. Just couldn't get all rid of it 😛 But yes Washing hands are 1#

  31. As an Australian, I have to say, colds happen more in Summer.
    I was always confused about that as a kid.

    We're also not told to go out in the cold in Winter at all.

    The dry air thing does work though. While yes, where I live in Australia, Summer is the wet season, airconditioning is a must for most people, and they will stay in airconned places, such as shopping centres with hundreds (sometimes thousands) of other people, and in their own homes (which aircons dehydrate). In Australia, it feels like being outside will kill you in Summer.

    So it's purely a Northern-Hemisphere thing to think colds only happen when it's cold, because we down here in Australia get it at the same time as you guys, probably from all your tourists infecting us.

  32. In Boston right now it's -2. wind chill of -20. Remember that next time you think you're cold. Happy new year everybody


  34. First part of video: Don’t go outside. Stay indoors where it’s humid
    Me:Got it
    Second part of video: Go outside. Inside is dangerous
    What do you want me to do, SciShow? Live in the door?

  35. In some parts of the world people also travel more during winter or are in malls more which means you're around more people, increasing your likelihood of getting a cold.

  36. huh. I always thought it was simply because of the temperature of the cold air that is being breathed in mixing with the warmth of the body makes the temperature perfect for infections to grow.

  37. I think the connection to drying out nose and throat lining makes sense. When I bike to class during the winter and breathe in cold air I almost ALWAYS get sick (whether that's viral, allergy related, or otherwise I can't say, but its always the same symptoms. Headache, congestion, fatigue)

  38. With the sunlight and cabinfever associations, it actually sounds like it's staying in, not going out in the cold, that make us sick. So, we need to reverse all our winter advice, and take more walks in the snow.

  39. No more colds. It's the nose silly. The Nose incubates colds. https://www.amazon.com/No-More-Colds-Search-Cure/dp/1534941738

  40. I always thought it was because the cold weather interrupted the homeostasis of the body and we got sick since hot weather kills bacteria but cold preserves it. 😱

  41. actually our immune systems are higher in the winter so some people like me are just allergic to the cold air and that never gets looked into for the rest they were probably stupid got the flu shot weakening their immune system so they became more likely to get sick and die

    thx for this ha bisky vid the only people i know whoever got sick in the winter were the morons that got the flu shot

  42. I got the impression that when our body is loosing heat, due to cold weather, it tries to warm itself up switching resources from defending against infections to maintaining constant body temperature. It just can't do both things as efficiently. This opens a path for viruses / bacteria to infect us.

    So, even though the temperatures outside is below 0C, which kills the things causing "cold/flu", once you loose body heat and walk into a warm cosy home, you're like an open door, inviting all the nice, sickness causing organisms to infect you.

  43. Tell that to government sheep. People get sick in the cold months period. Flu in the winter thats why they advertise flu shot in cold months

  44. The reason we have cold season is because the people with poor immunity get sick and then come around everybody else that isn't that have a good evening unity and sneeze all over them and touch everything people are disease they should stay

  45. And me that almost never wash my hand, doesn't avoid at all any risk of getting sick. And i never get sick.
    Well. I'm pretty sure if you keep your Immune system very active (which mean to not clean your hand every single time) you can survive much better against infection from all around.

  46. This video is quite faulty indeed. There is a serious research about flu affects and cold weather relationship: https://www.pnas.org/content/112/3/827#sec-1

    very very briefly, flu is related to viruses that's correct but it looks like that cold weather affects immune system and it affects how you deal with the flu.

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