Fight off those nasty change-of-season viruses with our natural prevention tips. Find out how to make over your medicine cabinet, brew herbal teas, and build up your resistance, and learn what to do when you're feeling under the weather.

While some contact with germs is a good thing -- it strengthens your immune system -- washing your hands is crucial for preventing illness; it's harder to catch a cold from kissing a sick person than it is from shaking his hand and then rubbing your eyes or nose. Antibacterial soap and piping-hot water aren't necessary; just apply soap to wet hands and rub vigorously for 15 seconds. (It's the scrubbing that matters.)

Research shows that sleep-deprived people produce fewer virus-fighting cells. And it's normal to sleep a bit more in winter; before we had electricity, people went to bed earlier and slept longer as the days got shorter. As often as possible this season, treat your immune system to an early bedtime.

Getting regular exercise helps your body avoid succumbing to illness in times of stress. But since too much exercise may lower immunity, aim for getting 30 minutes of daily physical activity: Try biking, walking, and even gardening or cleaning. If you're an athlete, take extra care to eat a nourishing diet (including plenty of slow-burning carbohydrates, protein, fruits, and vegetables).

Regular exercise keeps all your systems working, including your immune system. When possible, choose outdoor exercise because it decreases your exposure to crowds (and therefore germs). But even if you prefer your health club's treadmill, stay active.

Your body has its own thermostat that regulates temperature -- that's what goose bumps do. Overheated houses and workplaces can make this internal thermostat "lazy" and less effective. To keep your internal heating system in good working order, take "contrast showers" -- hot water followed by a blast of cold. Try starting with 5 seconds of cold water and working up to 30 seconds.

When you're run down, you become more susceptible to illness. Stress releases cortisol, which has direct, negative effects on your immune system. Balance your routine with regular doses of meditation, yoga, or slow, deep breathing.

Yoga's twists, backbends, and inversions stimulate important immunity components -- the adrenal glands and lymphatic system -- helping them perform better. Its deep breathing also helps calm the nervous system, which tells the immune system when to fight off a threat and when it can rest -- signals that can become garbled when you're tense. Try our immunity-boosting poses this season to help stave of the sniffles.

It's never too late to get vaccinated! Influenza puts people in a weakened state that can trigger a heart attack or stroke in vulnerable individuals. Additionally, studies show a relationship between annual flu shots and reduced risk of cardiovascular events.

Wipe down surfaces that get a lot of traffic, such as doorknobs, telephones, TV remotes, and the refrigerator door, with an all-purpose cleaner. Learn More: Green Cleaning

Encourage your family to place them in the dishwasher as soon as they're done to prevent another person from using them. Even if someone feels well, he or she could carry and spread germs for several days before getting sick.

Drink more water. A sore throat, often the first sign of an upper-respiratory virus, can be soothed by gargling with warm water mixed with antimicrobials such as salt or oil of oregano.