by prevention.com

Immunity is the season's magic word. When temperatures drop and windows and doors stay shut, viruses can thrive indoors; if your immune system isn't up to the task, you're likely to catch the latest bug to hit town. This means less energy, the possibility of health complications, and just plain old feeling awful. That's why it's essential to ward off the very real threat of colds, flu, and other scary winter germs lurking on every doorknob, in every public bathroom, and on every grab-rail of your morning train to work.

Each winter, these infections put millions of people out of commission, cost employers more than $20 billion in paid sick days, and send more than 200,000 sufferers to the hospital. So how do you protect yourself? We've compiled a list of exactly what you need—and what you should avoid—to stay healthy during cold and flu season. These ideas made the cut not because they have fancy names or pack 400% of your daily vitamin allowances, but because they're safe, they've proven their worth in clinical studies, and our trusted experts recommend them.

Get a flu shot

An influenza vaccination can reduce the risk of flu illness by 50 to 60% in the general population and can decrease the severity and side effects if you get sick. So roll up your sleeve—the government says that this year there will be plenty to go around; the feds recommend flu shots for everyone ages 6 months and older. The quadrivalent vaccine (which includes the nasal spray version approved for ages 2 to 49) inoculates against four different viruses and may offer better protection than the trivalent shot, which protects against three viruses. The best time to get inoculated is in October or November, a few weeks before flu season begins to peak, says Neil Schachter, MD, a professor of pulmonary medicine at Mount Sinai Medical Center and author of The Good Doctor's Guide to Colds & Flu.

Stock up on pens

Cold and flu germs are easily passed through hand-to-hand contact, says Schachter, so any way you can avoid touching public objects—such as the communal pen at the bank—will cut your risk. Having your own supply of dime-a-dozen plastic ballpoints might just keep you from picking up a virus. "When you get up in the morning, don't leave the house without a pen in your pocket or your purse," Schachter suggests. "Take it wherever you go—and use your own instead of the doctor's, the delivery guy's, or the restaurant waiter's."

Buy plenty of hand sanitizer

When researchers from Children's Hospital in Boston studied 292 families for 5 months, they found that those who carried hand sanitizer with them had 59% fewer cases of stomach bugs than nonusers. That's because, when used correctly—squirt out enough gel so your hands still feel damp after rubbing together for 10 to 15 seconds—these products nearly eliminate germs. A bottle stashed in your purse (and in your husband's briefcase and the kids' book bags) is an excellent alternative to washing if you've just shaken a bunch of hands and can't get to a sink.

Join a club

You know that friendships counteract the harmful effects of stress hormones, but new research says the more friends you have, the healthier you'll be. Carnegie Mellon doctors gave 83 college freshmen an influenza vaccine and found that those with larger social networks produced more flu-fighting antibodies than those who hung out in smaller groups. Students who reported feeling lonely produced fewer antibodies, as well. Start a book group or cultivate group-friendly hobbies.

Express yourself

A constructive argument with your spouse can actually increase immunity, say UCLA researchers. They asked 41 happy couples to discuss a problem in their marriage for 15 minutes. The researchers detected surges in blood pressure, heart rate, and immune-related white blood cells, all of which were similar to the benefits seen with moderate exercise. But you still have to play nice: Couples who frequently use sarcasm, insults, and put-downs have fewer virus-fighting natural killer cells, have higher levels of stress hormones, and take up to 40% longer to recover from injuries than those who manage to stay positive and affectionate during their quarrels.The worst thing you can do? Keep what's bothering you bottled up: People with a type D personality—those who keep their opinions and emotions hidden—have killer T cells that are less active than those found in more expressive peers.

Set goals

Challenging situations can work to your advantage: "When we're facing adversity, we become hyperalert and our bodies guard themselves against enemies—whether that's a predator or a virus," says Monika Fleshner, PhD, an associate professor of neuroimmunophysiology at the University of Colorado at Boulder. So, even though unresolved stress can make you sick by suppressing immunity, raising blood pressure, and increasing your risk of heart disease, the ups and downs of everyday life, such as working toward a deadline or a promotion, will actually provide a health boost. The best prescription is to set your sights on a reachable target, says Fleshner. At the beginning of each week, give yourself at least one challenge at your job that you'll aim to accomplish by Friday.

Sign up for a rubdown

Massage therapy has been shown to improve immune function and energy levels in cancer patients. In a 500-person review study, massage lowered cortisol levels by up to 53%. Experts believe this boost can extend even to those who are simply dealing with the daily pressures of life. A weekly kneading, whether it's a professional massage or simply a back rub from your significant other, can also increase serotonin and dopamine, mood boosters that may help protect your immunity, as well.

Take a daily multivitamin

Look for one with 100% of the recommended daily values of vitamins A, B6, B12, C, and D and the minerals chromium, copper, folic acid, selenium, calcium, and zinc. Take your multi during a meal that contains a bit of fat so you can absorb the nutrients better; a glass of water will help the pill dissolve.

Pop astragalus

This Chinese root—pills are available in health food stores—has a long track record as an immunity booster. Research suggests that it stimulates the bone marrow to produce more disease-fighting white blood cells, which in turn produce antibodies and interferon, an antiviral protein.
In a Chinese study, 3 to 4 months of astragalus injections raised lymphocyte (a type of white blood cell) activity by up to 45% in people who had a virus that can cause meningitis and heart inflammation. Other studies suggest astragalus's immune-stimulating compounds are also active when taken orally. To maintain disease-fighting levels of the herb in your system, use it for at least 3 months (up to 2 years at a time) for best results. Take two 500 mg capsules of dried astragalus root, 3 times each day.

Move more

University of South Carolina researchers discovered that men who got in 3 hours a day of moderate activity (the equivalent of walking briskly, climbing stairs, or playing tennis) were 35% less likely to catch a cold, compared with those who did only 1 hour. The good news? You may not have to breathe hard every day: UCLA researchers have found that tai chi, the Chinese art of slow movements, meditation, and breathing, decreases the release of catecholamine, a neurotransmitter that dampens the immune system; in one study, 3 sessions a week for 4 months enhanced immune cell function by 45% in adults with shingles.

Wash your hands—a lot

Researchers from the Naval Health Research Center in San Diego saw a decrease in respiratory illness of 45% from the previous year among 45,000 recruits who had been instructed to wash their hands at least 5 times a day (soap dispensers were installed, and the students were lectured monthly on the importance of hand washing). Similar results would be likely in schools, homes, and workplaces where regular hand washing is adopted, says William Schaffner, MD, chair of the preventive medicine department at Vanderbilt University School of Medicine. "I'm not talking about just before dinner," he adds. "We have a rule in my house: Anytime you walk in the door, you hang your coat and march to the sink to wash your hands." Such frequency may not be necessary for all families, but experts agree that simple soap-and-water hand washing is an easy and effective way to stay healthy year-round.

Turn in

Getting enough sleep is the most important thing to do this season, because any other precautions you take against cold or flu—the right food, supplements, even vaccinations—won't offer the same protection if your body's too tired to use them properly. University of Chicago researchers found that men who had slept only 4 hours a night for 1 week produced only half the amount of flu-fighting antibodies in their blood (jump-started by a flu shot), compared with those who slept 7 1/2 to 8 1/2 hours.