In the United States, most adults can expect to get at least two colds between September and March. Experts aren't certain why, but they believe it's because cold viruses survive best in cold, dry weather.
What's the best way not to get sick? Well, you can't keep the cold viruses from being all around you. But you can mount a series of defenses strong enough that they can't get to you. Here are the six top doctor-tested ways to keep colds away.
1. Fight off Colds by Embracing Your Inner Germophobe
Doctors and other medical professionals, who are on the front lines in the war against colds, have discovered ingenious ways to avoid touching hard surfaces that many other people have also touched (leaving behind cold viruses that can live for up to 24 hours). They open doors with their forearms, for instance, and push elevator buttons with their knuckles.
Train yourself to think in terms of public surfaces, which means anything other people touch. Yes, the handles of shopping carts are germ breeding grounds. But watch out for your own steering wheel as well, if there are several drivers in your family. Doorknobs and toilet seat lids are obvious concerns, and be alert for anything you touch or pick up, including the backs of chairs, the handles of suitcases, the books you share with friends. Can't remember where your hands have been in the last hour? Solve the problem by washing them frequently, especially after you've been in public locations. Carry disinfectant wipes to wipe down surfaces you have to touch and hand sanitizer for when you can't get to a sink.
2. Fight off Colds by Making Your Face off-Limits to Hands
Of the more than 200 viruses that cause the common cold, the majority are a type called rhinoviruses, the root of which is rhino, which means nose. Virus particles must make it into the mucous membranes lining the nose in order to cause infection; the nasopharynx -- where the nose meets the mouth -- is the "sweet spot" for these viruses. If they can reach this spot, it's very likely you'll get sick; if you prevent them from getting there, you won't. And a virus deposited at the base of the nose can easily be inhaled higher up into the nose. Virus particles can't easily reach the nose on their own, since they don't stay airborne for long; they need your hands to transport them there. Therefore, if your hands don't touch your mouth or nose, the virus has no way to hitchhike a ride.
One more thing most people don't realize: The eyes are connected directly to the nasal passages via the tear ducts. According to one humorous poster displayed in many doctors' offices, we're much more likely to catch a cold from putting an infected person's water glass in the sink and then wiping our eyes than we are from drinking from the glass itself. Keep your hands away from your nose and eyes, and you'll greatly reduce your chances of catching a cold.
3. Fight off Colds by Being Wary of the Sneeze
It may look funny -- even a tad uncouth -- when you see someone sneeze into the crook of their elbow, but they're doing you an enormous favor. Colds are spread by physical contact with tiny particles of virus, and when you sneeze, you send droplets of virus-filled mucous raining down onto any handy surface, including your hand if you've used it to cover your mouth. So do everyone, including yourself, a favor by training yourself and your family in the art of the elbow sneeze. As of January 2013, both the Red Cross and the Centers for Disease Control have introduced campaigns to teach people to carry tissues at all times, or to sneeze into their elbows to reduce the transmission of both colds and flu. (If you do use a tissue, make sure to dispose of it promptly. One study found that cold germs can live for several hours on tissues and other porous surfaces.)
4. Fight off Colds by Hydrating to Stay Healthy
When the mucous membranes in the nose and throat are moist, they're better equipped to fight germs. The best way to ensure moist nasal tissues? Be vigilant about staying well hydrated by drinking four to eight glasses of water throughout the day. For the same reason, many doctors recommend nasal mists and saline nasal sprays at the first sign of a cold. In some studies, they've been found to be effective in boosting the body's natural system of germ eradication, which works to flush germs from your nose.
Nasal membranes dry out even more easily in dry winter air, making them more susceptible to germs, which is one reason experts say we get most colds and flu during the winter. Drinking herbal tea is one good way to keep your protective mucous membranes working; the heat triggers your nasal passages to release moisture, and inhaling the steam bathes the tissues in moisture.
Another nourishing source of hydration and increasingly used cold remedy is bone broth.
"Bone broth contains amino acids such as glycine, proline and arginine that have powerful anti-inflammatory effects," says Sharon Brown, a clinical nutritionist and co-founder of Bonafide Provisions. "Arginine has been found to be beneficial for whole body inflammation and the amino acid, cysteine, is known for its ability to thin mucus."
5. Fight off Colds With Immune-Boosting Sleep
Researchers know something night owls just can't seem to accept: Those who cheat themselves of sleep are more likely to get sick. The reason? While you sleep, your body recharges your immune system, so it's better equipped to fight off a cold. It's a difficult causal link to establish, but one small study published in the Archives of Internal Medicine found that people who slept fewer than seven hours a night were three times more likely to develop a cold when exposed to a virus than those who slept eight or more hours per night. Experts don't know exactly how sleep protects you from getting a cold, but there's evidence that sleep boosts immune function by increasing the number of "killer cells," which attack viruses. So if you're among the 50 to 70 million people who the CDC estimates suffer from sleep problems, get help to get healthy.
6. Fight off Colds With Vitamins C and D
It's natural at this time of year to want to arm your immune system with some of the many vitamins and supplements that are touted as having immune-boosting properties. Unfortunately, most of them don't work. There are a couple of simple and inexpensive vitamins that are proven to boost immune function, though: vitamins C and D.
While taking Vitamin C won't necessarily prevent you from coming down with the cold or flu, it can help end your cold sooner if taken before symptoms come on, according to The Mayo Clinic.
Sarath Malepati, MD, creator of immune support supplement EZC Pak, points to research that shows Vitamin C plays an important role in healthy (or normal) immune system function. A healthy immune system can help keep colds and flu at bay.
"Vitamin C is critical to the healthy function of several immune cells involved in the clearance of viruses and bacteria and supports the mounting of immune responses to infections," says Malepati. "For healthy immune system function, women should aim to consume about 75 mg of vitamin C daily and men should try to get around 90 mg per day."
And when it comes to Vitamin D, studies show that most adults don't get enough Vitamin D from their diet alone. Experts don't yet know exactly how vitamin D protects against colds and flu, but numerous studies show a direct association between low blood levels of vitamin D and frequency of infection. Other research supports the idea that vitamin D boosts immune function in general.
How to know if you might need extra D? Ask yourself if you drink a lot of vitamin-D-fortified milk (one of the only food sources of this nutrient), live in the south, and spend at least 15 minutes a day outside in direct sunlight without sunscreen. (Remember, north of the 37th parallel, which runs just south of San Francisco in the west and just south of Richmond, Virginia, in the east, the sunlight simply isn't strong enough to trigger vitamin D production at all during the winter months.)
If not, chances are you're D-deficient. It's easy to have the level of vitamin D in your blood checked via a blood test. But a safer approach may be to take a vitamin D supplement no matter what, since there aren't any negative side effects to worry about unless you take a huge amount. The current Recommended Daily Allowance (RDA) for children and adults is 600 IUs (international units) daily; the RDA for those aged 71 and older is 800 IUs. Those with documented low levels may need to take higher doses. It's best to take it in the form of vitamin D-3, which is most easily absorbed.
Caring.com Editor Laura Dixon contributed to this article.