The most effective way to keep yourself from getting sick is layering several simple habits: washing your hands properly, sleeping enough, staying active, and keeping up with vaccines. No single strategy is bulletproof, but combining them creates a meaningful shield against the colds, flu, and other respiratory infections that circulate year-round.
Wash Your Hands for 20 Seconds
Proper handwashing reduces your risk of respiratory illness by 16 to 21%. That’s a significant drop from something that costs nothing and takes less than half a minute. The key word is “proper.” Scrubbing with soap for about 20 seconds removes substantially more germs than a quick rinse. Lather the backs of your hands, between your fingers, and under your nails. The friction matters as much as the soap.
The moments that matter most are before eating, after using the bathroom, after blowing your nose, and after being in public spaces where you’ve touched shared surfaces like doorknobs, handrails, or grocery carts. If soap and water aren’t available, an alcohol-based hand sanitizer with at least 60% alcohol works as a backup, though it’s less effective on visibly dirty hands.
Sleep Is Your Immune System’s Foundation
Cutting your sleep short does more than make you tired. Sleep deprivation triggers a surge of inflammatory signals throughout your body, the same types of molecules your immune system releases during a serious infection. When those signals are elevated chronically because you’re not sleeping enough, your immune system essentially runs in a stressed, disorganized state. It becomes less efficient at fighting off actual invaders when they show up.
Most adults need seven to nine hours per night. If you’re consistently getting six or fewer, you’re measurably more likely to catch a cold after being exposed to a virus. Prioritizing sleep during cold and flu season is one of the highest-return things you can do. That means keeping a consistent bedtime, limiting screens before bed, and treating sleep like the non-negotiable health behavior it is.
Exercise Helps, but More Isn’t Always Better
Regular moderate exercise boosts immune function above what you’d have as a sedentary person. Walking briskly, cycling, swimming, or jogging at a comfortable pace all count. The relationship between exercise and immunity follows a J-shaped curve: moderate activity strengthens your defenses, but pushing into extreme territory can temporarily suppress them.
The immune dip becomes most pronounced when exercise is continuous, lasts longer than 90 minutes, hits moderate-to-high intensity (think 55 to 75% of your maximum effort), and you haven’t eaten beforehand. This is mainly relevant for endurance athletes training for marathons or similar events, not for someone doing 30 to 60 minutes of daily activity. For most people, the message is straightforward: move your body regularly and you’ll get sick less often.
Get Your Flu Shot Each Year
Flu vaccines aren’t perfect, but they provide real protection. For the 2024-2025 season, preliminary CDC data shows the vaccine reduced outpatient flu illness by roughly 42 to 56% in adults, depending on the monitoring network. For children, effectiveness ranged from about 59 to 63% for outpatient visits and up to 78% for preventing hospitalization. Even in adults 65 and older, who typically respond less strongly to vaccines, effectiveness against hospitalization hovered around 38 to 57%.
The vaccine works better against some flu strains than others. Protection against H1N1 strains tends to be stronger than against H3N2, which mutates more rapidly. But even partial protection matters. Vaccinated people who do catch the flu generally experience milder symptoms and recover faster. Getting vaccinated in September or October gives your body time to build antibodies before peak season hits in the winter months.
Keep Indoor Humidity Between 40% and 60%
The air inside your home affects how easily respiratory viruses spread. Research backed by the National Science Foundation found that maintaining indoor relative humidity between 40% and 60% is associated with lower rates of respiratory infections. Conditions outside that range, either too dry or too humid, are linked to worse outcomes.
Dry winter air (common when heating systems run constantly) lets virus-carrying droplets hang in the air longer and can dry out the mucous membranes in your nose and throat, weakening your first line of defense. A simple hygrometer (available for under $15) lets you monitor humidity levels, and a humidifier can bring dry rooms into the sweet spot. On the flip side, humidity above 60% encourages mold growth, so balance matters.
Zinc Lozenges Can Shorten a Cold
If prevention fails and you feel a cold coming on, zinc lozenges started within the first 24 hours of symptoms can cut the duration of illness by about a third. The effective dose in clinical trials was more than 75 milligrams of elemental zinc per day, spread across multiple lozenges. Both zinc acetate and zinc gluconate forms worked, and the typical treatment course lasted one to two weeks without serious side effects.
The important detail is timing. Zinc lozenges work best when you start them at the very first sign of a scratchy throat or sniffles. Waiting two or three days in significantly reduces the benefit. Check the label for the amount of elemental zinc per lozenge, not total zinc compound weight.
Probiotics and Gut Health
Your gut houses roughly 70% of your immune cells, so what happens there affects your ability to fight off respiratory infections. Several probiotic strains have clinical evidence for reducing either the frequency or duration of colds and upper respiratory infections. The most studied is Lactobacillus rhamnosus GG, which has been shown to reduce rhinovirus infections in adults and lower the incidence of respiratory illness in children. Other strains with positive trial data include L. casei Shirota (reduced frequency and duration of upper respiratory infections in working adults), L. plantarum L-137 (fewer infections in people under high stress), and L. paracasei N1115 (stronger resistance to respiratory infections in older adults).
Combination formulas also show promise. A blend of L. paracasei, L. casei 431, and L. fermentum PCC strengthened resistance to common cold and flu-like infections in adults. Another combination of L. gasseri and B. longum reduced the duration of respiratory illness episodes and fevers. You can get these bacteria through fermented foods like yogurt, kefir, and kimchi, or through targeted supplements. If you go the supplement route, look for products that list specific strains (not just species names) and contain at least one billion colony-forming units.
Vitamin D: Useful but Uncertain
Vitamin D plays a role in immune cell function, and people with very low levels do appear more susceptible to respiratory infections. However, the NIH notes that evidence for vitamin D’s effect on infection resistance remains “inadequate or too contradictory” to establish firm recommendations beyond bone health. There’s no agreed-upon optimal blood level for immune function, and it likely varies by age, ethnicity, and individual biology.
If you live in a northern climate, have darker skin, or spend most of your time indoors, you’re more likely to have low vitamin D levels, and correcting a genuine deficiency is reasonable. A blood test can tell you where you stand. Beyond that, megadosing vitamin D specifically to prevent colds isn’t well supported by current evidence.
Masks Still Work in High-Risk Settings
When respiratory illness is surging in your community, wearing a mask in crowded indoor spaces adds a layer of protection. Not all masks perform equally, though. In real-world testing with fine aerosol particles (350 nanometers, roughly the size range relevant for airborne viruses), N95 respirators filtered about 54% of particles, while N99 masks filtered about 90.5%. Both fell below their rated efficiency because lab conditions differ from how people actually wear masks, with gaps around the nose and cheeks letting unfiltered air through.
Fit matters more than the mask’s rating on the box. A well-fitted N95 outperforms a loosely worn one by a wide margin. If you’re in a high-risk situation (visiting someone who’s sick, flying during flu season, or spending time in a crowded waiting room), pressing the nose wire firmly and ensuring the mask sits flush against your face makes a real difference.
Putting It All Together
No single habit makes you invincible. The people who get sick least often tend to stack these behaviors: they sleep seven-plus hours, wash their hands consistently, stay physically active at a moderate level, get vaccinated, and pay attention to indoor air quality. During cold and flu season, adding probiotics and keeping zinc lozenges on hand gives you additional tools. Each layer on its own provides modest protection. Together, they make a meaningful difference in how many sick days you log each year.