Old wives tales about colds: reality or fantasy?
Will getting cold make you sick?
It is winter here in the Northeast! Recently, I heard myself tell my daughter not to go out with her hair wet or she would catch a cold 😱. Wait, what? Did I say that? The minute I said it, I thought, wait a minute, there is no scientific evidence backing this up! Am I spreading old wives tales about colds? Is this fake news?
I think probably, most of us, have heard the infamous phrases. It’s cold outside, wear your jacket or you will catch a cold. Dry your hair before you go out into the cold or you will get sick. There are so many variations of this, across generations and cultures. I’ve heard these phrases in both Spanish and English, in various countries. Furthermore, the phrase has been used for centuries. So, it must be true, right? 😜 Well, I think it is worth exploring the phrase and investigating if this is indeed scientifically based.
Let’s look at some facts about getting ill and the influence of our environment.
There are seasonal variations to cold producing viruses
For example, rhinovirus, which is the main culprit for the common cold, occurs predominantly in the spring and fall season. Meanwhile, Influenza (responsible for the Flu) shows up mostly during the winter months. Why? Well, various cold causing organisms thrive best in the lower temperatures we have in fall and winter. This is well known, and it is certainly a contributing factor to our seeing more colds when the weather gets cooler.
Hypothermia lowers your immune function
Hypothermia, which is an extreme lowering of your core body temperature, results in multiple effects in our body. One of which is decreased immune system function. As you may recall, our immune system is responsible for fighting infections. When it doesn’t work well, infections can take over.
Our nose is one of the primary gateways for the development of respiratory infections. There are many blood vessels inside our nose. These vessels are like the “highway” that bring many of the cells that fight infection to keeps us safe. When it is very cold, those blood vessels in our nose constrict and therefore the blood flow to our nose lessens. Our little infection fighting “soldiers” can’t get to where they need to be. This is thought to be a contributing factor to the development of viral infections in the cold.
However, any decrease in body temperature is not the same. Several studies suggest that a mild decrease in core temperature (about 0.5 °C) has little effect or even a stimulatory effect on immune function. However, modest (about 1 °C) and severe (about 4 °C) decreases in core temperature may inhibit immune function.
What does this translate to? That you would have to be really cold and likely for a prolonged period of time for cold temperature to have an effect in your immune system.
Dry air can may impair the immune function in your nose by drying your nasal mucosa
Another interesting study, looked at people exercising in places with low humidity. They noticed that their nasal mucosa (the “skin” inside our noses) became very dry. As people exercise, they inhaled large volumes of this dry air. This, they noticed, lead to damage of that tissue inside the nose (for example, we get nose bleeds more often in cold, dry weather).
Furthermore, our respiratory tract is lined up with little hair like structures called “cilia”. These cilia move up and down to help us clear mucous and any “invaders” that get stuck to the mucous and try to get us. Exposure to dry air lowers the movement of the cilia. This, together with a dry, damaged nasal mucosa makes it easier for a virus to breach our system and wreak havoc.
Also interesting, when we look at illness and humidity together, there is another study that researched guinea pigs. This study further supports the effect of humidity on cilia and the influence of temperature on influenza virus spread.
The study found that low relative humidity of 20%–35% were most favorable for viral transmission. However, transmission was completely blocked at a high relative humidity of 80%. Additionally, when guinea pigs were kept at 5 °C, transmission occurred with greater frequency than at 20 °C, while at 30 °C, no transmission was detected.
The authors of this research implicated that low relative humidity produced by indoor heating and cold temperatures as features of winter favored influenza virus spread.
Some people wheeze when it is cold
For people who suffer from asthma, there is a subset of patients who will have a flair in their asthma when exposed to the cold. This is called “cold induced asthma” and these patients will get sick with asthma (not a cold, though), when exposed to cold air.
During winter, we spend more time indoors
When it is cold outside, we tend to spend more time indoors, with windows closed and in close quarters with others. That within itself makes the spread of respiratory illnesses easier and it is yet another reason why we tend to get sick more often during the winter months.
So, what is the bottom line, do we believe the old wives tales about colds?
Well, it would appear there is grain of truth to what grandma used to say, but it is not that simple. You have to have a series of events line up to predispose you to illness.
While exposure to extreme cold temperatures or the dry, winter air for prolonged periods may decrease our immune function and, if exposed to a virus, make it easier for us to contract a cold, it is also not true that just merely being cold will make you sick. You would have to experience extremely cold weather (enough to decrease your body temperature) AND be exposed to a virus.
For people who have cold induced asthma, yes, being exposed to the cold will make them sick, but not from a virus. They will be sick from their intrinsic problem with asthma.
Stay healthy and warm this cold and flu season!