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If every tickle in your throat, slight headache, or mild cough sets off alarm bells these days, you’re not alone. It can be tricky to tell the difference between a cold, the flu, and Covid-19.
Some clues: A cold is likely to cause mild symptoms like a runny nose, sore throat, or cough. If you have body aches and a fever that came on quickly, you may have the flu.
Covid-19 can be harder to pin down. Fever, cough, headache, shortness of breath, and an inability to taste or smell are among the symptoms, but some people who are infected have none of those.
Not sure if you should get tested or call your doctor? Try googling “CDC coronavirus self-checker” for help.
The good news: Simple precautions that can curb the spread of Covid-19—like wearing a mask, social distancing, and frequent hand washing—can also lower your risk of catching a cold or the flu. Just don’t put much stock in “immune boosting” claims about foods or supplements.
Can anything soothe symptoms or shorten your illness? Here’s what we know.
Vitamin D
Claim: “Vitamin D can help reduce Covid-19 risks,” declared Healthline.com in September.
Evidence: An analysis of 25 randomized trials on roughly 11,000 people reported about a 20 percent lower risk of colds and flu in those who took vitamin D daily or weekly.1 The researchers calculated that 20 people would have to take vitamin D to prevent one cold or flu infection.
Vitamin D had the biggest impact in people with deficient blood levels (below 10 nanograms per milliliter).
But those studies looked at colds and the flu, not Covid-19.
Some studies have reported a link between low vitamin D and the risk of getting Covid-19. For example, among 489 people, those whose levels were inadequate (below 20 ng/mL) were 77 percent more likely than people with normal levels to test positive for Covid.2
That kind of study can’t prove that vitamin D protects against Covid-19. Something else about people with low vitamin D could explain their higher risk.
“We need well-designed trials to determine whether vitamin D supplements are effective for preventing or treating Covid-19,” says JoAnn Manson, chief of preventive medicine at the Harvard-affiliated Brigham and Women’s Hospital in Boston.
Fortunately, dozens of trials—including one by Manson—are looking at whether vitamin D can lower the risk of getting Covid or its severe outcomes.
Bottom Line: Until we know more, “everyone should avoid being vitamin D deficient,” says Manson. Since few foods are rich in D, take a multivitamin or vitamin D supplement with roughly the RDA (600 IU a day up to age 70 and 800 IU over 70).
1BMJ 2017. doi:10.1136/bmj.i6583.
2JAMA Netw. Open 3: e2019722, 2020.
Over-the-Counter Drugs
Claim: “With Mucinex All in One, you’ve got unbeatable relief from your worst cold and flu symptoms,” says the TV ad.
Evidence: If you don’t need a fever and pain reducer and a cough suppressant and an expectorant and a nasal decongestant, you’re exposing yourself to drugs—and side effects—you may not need if you take a combination cold-and-flu formula like Mucinex All in One.
Cough suppressants and expectorants (which thin mucus and make it easier to cough) can cause dizziness. Decongestants can raise blood pressure and may cause restlessness and insomnia. Fever and pain reducing non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen (Motrin, Advil), naproxen (Aleve), and aspirin can increase the risk of stomach ulcers over the long term.
Then there’s acetaminophen (Tylenol). Taking more than 3,000 milligrams a day over the long term can damage your liver. And acetaminophen is in so many cough, cold, allergy, pain, and sleep medications that it’s easy to end up taking more than you realize.
One bit of good news: If you’re steering clear of ibuprofen because of news reports last March warning that it can worsen Covid-19, relax.
Those warnings spread when a letter to a medical journal suggested that ibuprofen may increase the number of receptors that the virus binds to on cells.1
Since then, studies have reported no worse outcomes in Covid patients who take ibuprofen.2 And the World Health Organization quickly retracted its initial warning about using the drug for Covid symptoms.3
Bottom Line: Take cold and flu medicines when you need them, but don’t overdo it. And don’t give them to children under the age of six.
1Lancet Respir. Med. 2020. doi:10.1016/S2213-2600(20)30116-8.
2Clin. Transl. Sci. 2020. doi:10.1111/cts.12904.
3 twitter.com/who/status/1240409217997189128.
Honey
Claim: “Powered by the best of nature to help relieve your cough,” says the Robitussin ad featuring its new line of Naturals Cough Relief syrups made with honey and ivy leaf.
Evidence: In the largest study (partly funded by the honey industry), Israeli researchers randomly assigned 270 children with a cough due to a respiratory infection like a cold or the flu to swallow half a tablespoon of one of three kinds of honey or a placebo 30 minutes before bed.
Symptoms like cough frequency and severity and sleep quality improved by about half in all three groups of honey takers versus by about a third in the placebo takers.1
No good studies have tested honey in adults.
Bottom Line: The evidence that honey can relieve a cough due to a cold or the flu is pretty thin. And honey has a downside: Each tablespoon has 17 grams of sugar. That’s a third of the Daily Value for added sugar.
Chicken Soup
Claim: “Studies show [chicken soup] clears nasal passages and congestion better than other hot liquids,” reported WebMD in June.
Evidence: Only one study has looked. Fifteen healthy adults without a cold or the flu drank chicken soup, hot or cold water, or nothing on separate days. Five minutes after they sipped the chicken soup or hot—but not cold—water, their nasal mucus moved more quickly than when they drank nothing. But when they used a straw, only the soup sped up mucus.1
One tiny study, on people without a cold or the flu who knew what they were drinking, is pretty weak evidence.
Ditto for an oft-cited study in which chicken soup slowed the movement of neutrophils in test tubes.2 (Neutrophils are immune cells that cause inflammation when you’re fighting a respiratory infection.) So what? Chicken soup is digested long before it reaches your immune cells.
Bottom Line: Studies have never tested chicken soup on people with colds. But any hot liquid (including chicken soup) may help clear nasal passages.
1Chest 74: 408, 1978.
2Chest 118: 1150, 2000.
Echinacea & Elderberry
Claim: “Fast-acting formula for supporting immune response at onset,” says gaiaherbs.com about its Quick Defense, a supplement made with echinacea and elderberry.
Evidence: In the largest and best study on echinacea (co-authored by an employee of an echinacea maker), researchers randomly assigned 359 people to take echinacea or a placebo at the first sign of cold symptoms. The echinacea takers took 10,200 milligrams the first day and 5,100 mg a day for the next four days.1
Their colds were no shorter, and their symptoms were no milder, than those of the placebo takers.
In the best elderberry study, researchers offered the antiviral drug Tamiflu to 85 adults and children at the first signs of flu symptoms. (Tamiflu and other antiviral flu drugs can shorten the length of a flu by about a day, though most cases only last about a week.)
The researchers randomly assigned the volunteers to swallow either one tablespoon of the elderberry syrup Sambucol or a placebo four times a day for five days.2 (Children took just one tablespoon twice a day.)
Flu symptoms lasted just as long whether people took Sambucol or the placebo.
Bottom Line: Don’t expect much relief from echinacea or elderberry supplements.
1Ann. Intern. Med. 153: 769, 2010.
2J.Gen. Intern.Med. 2020. doi:10.1007/s11606-020-06170-w.
Dairy
Claim: “Milk is another food to stay away from when you’re feeling under the weather,” said the Eat This, Not That website in October, in an article about foods to avoid when you have a cold or the flu. “Dairy can temporarily thicken mucus.”
Evidence: In the only study to look at dairy in people with a cold, researchers infected 51 Australian adults with a cold virus, then asked them to keep track of how much dairy they ate or drank. (The study was partly funded by the dairy industry.)
Over the next 10 days, dairy intake wasn’t linked to “nasal secretion weights” (the scientists weighed the participants’ used tissues) or symptoms like cough, congestion, or runny nose.1
Other studies didn’t even look at people with colds.
In one (it was industry funded), researchers randomly assigned 125 Australian adults without a cold to drink 10 oz. of flavored cow’s milk or soy milk. Both groups reported that their saliva felt thicker and that they felt a coating in their mouths and throats.2 Could some people mistake that “coating” for mucus?
And in another, researchers randomly assigned 108 British adults who reported high levels of mucus (but had no cold) to drink 12 oz. of flavored cow’s milk or soy milk for four days. The soy milk drinkers reported about a 10-point drop (on a 100-point scale) in mucus secretion, while the cow’s milk drinkers reported about a 2-point drop.3 Not exactly a home run.
Bottom Line: Cold or no cold, there’s no strong evidence that dairy means more mucus.
1Am. Rev. Respir. Dis. 141: 352, 1990.
2Appetite 20: 61, 1993.
3Laryngoscope 129: 13, 2019.
Neti Pots
Claim: “If you feel like your allergies, sinus, and upper respiratory problems are escalating, it might be time to try a nasal irrigation device, such as a neti pot,” said EverydayHealth.com in 2018.
Evidence: In several studies in people with allergies or chronic sinus inflammation, rinsing out the nose with saline (using a nasal spray, neti pot, syringe, or other nasal irrigator) one to four times a day eased congestion by clearing out thick mucus and debris like dust and pollen.1,2 But most of the studies were small and not double-blind.
No good studies have tested whether a saline rinse can ease congestion in people with a cold or the flu.
If you decide to try a neti pot, make your saline solution only using store-bought distilled (not spring) water or tap water that’s been boiled for at least three minutes and then cooled.
Tap water that hasn’t been boiled can be contaminated with an amoeba that can pass through the nasal passage to the brain and cause a rare, but deadly, infection. (Drinking tap water is safe. You can only get the infection through your nose.)
Bottom Line: There’s no good research showing that irrigating your nose with salt water will help ease congestion if you have a cold or the flu.
1Cochrane Database Syst. Rev. 6: CD012597, 2018.
2Otolaryngol. Head Neck Surg. 2015. doi:10.1177/0194599815572097.