Avoid These 10 Immune System Snags By the Editors of Prevention.com Staying healthy isn't just about using hand sanitizer and avoiding coughing co-workers. It turns out some pretty surprising daily habitsâlike how you fight with your husband or whether you stay up late for Lettermanâcan impact how well your body fends off colds, flu and other pesky bugs. Here's a list of science-backed tips to add to your stay-healthy arsenal today. Find Out If Your Immune System Needs a Boost Don't Avoid the Water Cooler Friendship may be Miracle-Gro for your immune system. Research shows that the fewer human connections we have at home, at work, and in the community, the likelier we are to get sick, flood our brains with anxiety-causing chemicals, and live shorter lives than our more sociable peers. In one study, researchers who monitored 276 people between the ages of 18 and 55 found that those who had 6 or more connections were 4 times better at fighting off the viruses that cause colds than those with fewer friends. Don't let a jam-packed workday or hectic schedule get in the way of your friendships. Stop by a co-worker's office for a quick Monday morning catch-up, or e-mail/text your friends at night to stay in touch when you're too busy for phone calls. Don't Lose Sleep Scrimping on sleep has a powerfully detrimental effect on immunity. The perfect example: college students who get sick after pulling all-nighters cramming for exams. Poor sleep is associated with lower immune system function and reduced numbers of killer cells that fight germs. In fact, University of Chicago researchers found that men who had slept only 4 hours a night for 1 week produced 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. Most adults need between 7 and 9 hours of uninterrupted rest every night, but how you feel in the morning and throughout the day may be a better gauge. If you're tired when you wake up in the morning, you're not getting enoughâsleep, or maybe not enough quality sleep. Is It Exhaustion or Something More? 19 Bizarre Home Remedies That Work Total Body Shape Up Get a Healthier Heart in 28 Days Free: Your Ultimate Grocery Store Guide Don't Be a Debbie Downer Studies show that glass-half-empty types don't live as long as those who look on the bright side. When pessimists put a more positive spin on the calamities in their lives, they have less stress and better health. A classic UCLA study found that law students who began their first semester optimistic about the experience had more helper T cells mid semester, which can amplify the immune response, and more powerful natural killer cells, than students who had a more pessimistic perspective. One reason could be that optimists take better care of themselves. It could also be due to less stress-related damage to the immune system, such as killer cells that suddenly become pacifists. Personality is tough to change, look for reasonsâhowever smallâto feel lucky every day. Sounds hokey, but try striking up a dinner table conversation with your family where you all share a couple of good things that happened every day. Don't Bottle Up Your Moods 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. Don't keep what's bothering you bottled up. People with type D personaliesâthose who keep their opinions and emotions hiddenâhave killer T cells that are less active than those found in more expressive peers. 10 Silent Signals You're Too Stressed Don't Get Too Stressed Chronic stressâthe day-after-day kind you experience over job insecurity or a sick relativeâtakes a toll on many aspects of your health, including immunity. There is compelling scientific evidence that this kind of stress (as opposed to the every-now-and-again kind from a bad day at work or a screaming match with your kid) causes a measurable decline in the immune system's ability to fight disease. Periods of extreme stress can result in a lower natural killer cell count, sluggish killer T cells, and diminished macrophage activity that can amplify the immune response. In fact, widows and widowers are much more likely to get sick during the first year after their spouse dies than their peers who have not experienced a major loss. We're not going to tell you to take a bath or light a scented candle (unless those really help you relax, that is!). Do find go-to, healthy stress relievers that can take the edge offâbe it a long run on the treadmill, a relaxing yoga class, or baking dessert just for fun. The important thing is that you unwind and recover from stress, since it's often hard to avoid in the first place. Don't Borrow When You Can Carry Having your own supply of dime-a-dozen plastic ballpoints might just keep you from picking up a virus. Cold and flu germs are easily passed through hand-to-hand contact, says Neil Schachter, MD, a professor of pulmonary medicine at Mount Sinai School of Medicine and author of The Good Doctor's Guide to Colds and Flu. Any way you can avoid touching public objects -- such as the communal pen at the bank -- will cut your risk. "When you get up in the morning, don't leave the house without a pen in your pocket or your purse," Schachter suggests. Take your own wherever you go, and use it instead of the doctor's, the delivery guy's, or the restaurant waiter's Don't Drive Everywhere One in four American women doesn't exercise at allâand that's an easy way to set yourself up for sickness. When researchers compared inactive people with those who walked briskly almost every day, they found that who didn't walk took twice as many sick days in 4 months as those who strolled regularly. Experts say that it takes a 30 minutes of aerobic exerciseâa brisk walk countsâto sweep white blood cells back into circulation, making your immune system run more smoothly. Don't Hang Around When Friends Smoke We don't need to tell you that puffing ciggies is terrible for the entire body. But the secondhand kind is almost as harmful. Each year, because of exposure to tobacco smoke, an estimated 3,000 nonsmoking Americans die of lung cancer and 300,000 children suffer from lower respiratory-tract infections. Secondhand smoke can trigger an asthma attack and aggravate symptoms in people with allergies. In addition, tobacco smoke has been shown to make asthma worse in preschool children and may even cause it. Sounds obvious, but avoid secondhand smoke as much as you can -- including spending time with people while they smoke. Encourage anyone in your everyday life (husband, coworkers or neighbor friends) to quit. Don't Reach for Antibiotics Taking antibiotics at the first sign of a sniffle can make you resistant to these drugs over time, causing more serious infections. Researchers found that certain patients taking antibiotics had reduced levels of cytokines, the hormone messengers of the immune system. When your immune system is suppressed, you're more likely to develop resistant bacteria or become sick in the future. Take antibiotics only for bacterial infections, use them right away, and take the entire course. Don't use antibiotics preventively unless prescribed by your doctor, and don't save or share unfinished courses. Don't Be Little Miss Serious Consider this a doctor's note to troll YouTube on your lunch break... Researchers have found that the positive emotions associated with laughter decrease stress hormones and increase certain immune cells while activating others. In a study conducted at Loma Linda University School of Medicine, healthy adults who watched a funny video for an hour had significant increases in immune system activity. Um, laugh more. You know how: Watch your favorite comedies, have lunch with a pal known for her funny bone, and read those silly forwards from friends before you auto-click "delete."