Here's what scientific evidence says about some of the more pernacious popular myths about that seasonal affliction, the common cold:
1) Cold doesn’t give you a cold
How often did you hear this as a child: “Put on a sweater! You’ll catch a cold!”
Sorry, Mom: The conventional medical wisdom nowadays is that cold weather doesn’t directly make you get a cold. The reason we see more colds in chillier seasons, researchers say, is due to a number of indirect influences. The rhinoviruses that cause colds survive better in the drier air of winter. It’s also possible, according to the National Institute of Allergy and Infectious Diseases, that cold weather dries out the inside of your nose and leaves you more vulnerable to a viral infection. Plus, in cold months, people are driven inside, where they’re more likely to pick up viruses from other people. (According to the Mayo Clinic, in warmer climates where people aren’t being driven indoors, colds are more frequent in the rainy season.)
Still, “since the 1950s, a few studies have even provided scientific evidence [that chills don’t directly cause colds], finding that groups of volunteers who were exposed to infectious mucus and then forced to sit in frigid rooms caught colds at the same rates as warm control groups,” the New York Times reported in 2005.
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However, there are some small experiments that suggest a chill can make you more susceptible to the rhinoviruses that kick-start your seasonal sniffles.
Two researchers from Cardiff University’s Common Cold Center did find some evidence that chilling can raise one’s likelihood of catching a cold. In an experiment published in the journal Family Practice in 2005, scientists Claire Johnson and Ronald Eccles recruited 180 volunteers. Half the subjects placed their bare feet in a bowl of cool water (about 10 degrees Celsius, or 50 degrees Fahrenheit) for 20 minutes. The control group kept their shoes and socks on, and placed their feet in an empty bowl for 20 minutes.
Of the 90 people that received the chilled foot treatment, 13 said they were suffering from a cold four to five after the experiment. Meanwile, just five out of 90 of the control group participants developed a cold.
Johnson and Eccles couldn’t quite explain these results, but theorize that cooling the body causes the blood vessels of the nose and upper airway to constrict in a way that inhibits the natural defenses of the body. Thanks to this lowering of the defenses, someone with an immune system that’s successfully fighting off the cold virus sees their infection blossom into cold symptoms – so the theory goes.
2) Chicken soup really is good for you
Grandmothers everywhere were vindicated in 2000, when University of Nebraska Medical Center researcher Stephen Rennard published a paper in the journal Chest (also notable as one of the few scientific papers that contains a recipe). Rennard and his colleagues whipped up three batches of soup and analyzed them in the laboratory.
They found that chicken soup contains several substances that help ease cold symptoms. When chicken soup was added to human immune system cells called neutrophils, it inhibited the cells’ movements. While that might seem counterintuitive, keep in mind that most of your cold symptoms stem from your immune system response to an infection, not the virus itself.
It’s not clear exactly which ingredients in chicken soup are responsible for its cold symptom-fighting abilities, but researchers think there must be something in the combination of vegetables and chicken that packs a wallop.
An even earlier study published in Chest [PDF] points to chicken soup’s virtues. In 1978, a trio of researchers at Mount Sinai Medical Center in Miami Beach compared chicken soup to hot water in easing nasal congestion in 15 subjects. Hot water and chicken soup both helped unblock stuffy noses (or, in the words of the scientists, “increased nasal mucus velocity”), while cold water actually had the opposite effect of decreasing mucus flow. Chicken soup got the snot moving even faster than hot water – possibly due to some additional stimulation caused by the aroma or taste of a nice cup of “Jewish penicillin,” the researchers speculated.
3) You can't steam out cold symptoms.
The enemy of a cold must be heat, right? Not so fast. While it’s a folk remedy to cure a cold by breathing steam, a review of laboratory studies show that there’s little strong evidence that sniffing hot air can cure the sniffles.
In a review of six trials of steam treatment for the Cochrane Database, two researchers found little compelling consensus that inhaling steam helps drain congested noses or destroy cold viruses. Three of the trials reviewed showed a benefit, but didn’t move the needle on symptoms very far. Some studies showed that symptoms got worse after steam inhalation; others found simply no effect when comparing steam-treated cold sufferers to placebo groups.
“Steam inhalation has not shown any consistent benefits in the treatment of the common cold, hence is not recommended in the routine treatment of common cold symptoms until more double-blind, randomized trials” are conducted, the authors said.