4 Secrets to Never Getting Sick

Common wisdom has it that staying indoors, where it's warm and toasty, is easier on your immune system than being outside in the cold. Problem is, being inside puts you in close constant contact with other people—and their germs.

Not only does escaping into the fresh air give you a break from all those germs circulating inside, but going for a stroll can actually boost your immunity. "Exercise leads to an increase in natural killer cells, neutrophils, and monocytes, which ultimately increases immune function," says Ather Ali, ND, MPH, assistant director of Complementary/Alternative Medicine Research at the Yale-Griffin Prevention Research Center.

RELATED: How a Rock Climbing Trip Taught Me How to Trust

There are a trillion reasons why taking time to chill out might be the last item on your to-do list. But here's why it should be a priority: "Being stressed will increase your susceptibility to catching a cold," says Ali. That may be because, over the long term, it leads to the ongoing release of stress hormones, such as glucocorticoids.

These impede your body's ability to produce cell-signaling molecules called cytokines, which trigger a disease-fighting response from your immune system. "You're also less likely to take care of yourself—get ample sleep, eat right, exercise—when you're stressed," says Ali, which is crucial to upping your immunity.

RELATED: 2-Minute Yoga Flow to Stretch and De-Stress

Cold and flu can spread all too easily through touch. Keep your fingers away from your eyes, nose, and mouth as much as possible, and make sure to master the art of hand-washing. Soap and water remain your most effective tools there, according to the Centers for Disease Control and Prevention.

Germs can grow on bar soaps, so use the pumped kind—or better yet, a hands-free dispenser and choose regular soap over antibacterial. Lather for a solid 20 seconds before rinsing, and make sure to dry thoroughly (but not on your germy clothes!): "Damp hands are far more likely to spread bacteria than dry ones," says Dana Simpler, MD, a primary care physician at Mercy Medical Center in Baltimore.

RELATED: The 5 Dirtiest Things You Touch Every Day

An occasional restless night is nothing to worry about, but a continuous lack of zzz's can hamper your immune system's ability to function. Though experts often say that sleep requirements vary by individual, a 2009 Carnegie Mellon study found that anything short of seven hours nearly triples your odds of catching a cold—and that means seven straight hours, with no middle-of-the-night wake-ups.

"For many of us, the only quiet time we have to think through things is when we're lying down at bedtime. Unfortunately, problem-solving in bed interferes with sleep," says Leslie Swanson, PhD, a sleep specialist at the department of psychiatry at the University of Michigan, Ann Arbor.