Staying healthy comes down to a handful of habits that strengthen your body’s defenses and reduce your exposure to the viruses and bacteria that cause most common illnesses. None of them are complicated, but the details matter more than most people realize. Here’s what actually works, backed by the strongest available evidence.
Wash Your Hands for a Full 20 Seconds
Handwashing is still the single most effective thing you can do to avoid picking up infections. Soap doesn’t just rinse germs away. Its surfactants physically lift microbes off your skin, and the scrubbing action dislodges pathogens that water alone can’t remove. The CDC recommends scrubbing for at least 20 seconds because shorter washes leave significantly more germs behind. That’s roughly the time it takes to hum “Happy Birthday” twice.
The moments that matter most: after using the bathroom, before eating or preparing food, after blowing your nose, and after touching high-contact surfaces in public spaces like door handles, elevator buttons, and subway poles. When soap and water aren’t available, an alcohol-based hand sanitizer with at least 60% alcohol is a reasonable backup, though it’s less effective against certain pathogens like norovirus.
Sleep Is Your Immune System’s Foundation
Cutting sleep short doesn’t just make you tired. It measurably weakens your ability to fight off infections. In one study, people who slept only four hours a night for six days produced more than 50% fewer antibodies in response to a flu vaccine compared to people who slept normal hours. That’s a dramatic reduction in the very immune response your body needs to recognize and neutralize viruses.
Even a single night of sleeping just four hours triggers a spike in inflammatory signaling molecules that, over time, contribute to both immune dysfunction and chronic disease. Most adults need seven to nine hours per night for their immune systems to function well. If you’re regularly getting less than six, you’re leaving your defenses significantly compromised.
Move Your Body, but Don’t Overdo It
Moderate exercise is one of the most reliable ways to keep your immune system active. Even 15 minutes of moderate-intensity activity can mobilize natural killer cells, a type of immune cell that patrols your body for virus-infected cells and destroys them. A 30-minute walk increases circulating neutrophils, white blood cells that serve as your body’s first responders against infection. These cell counts return to baseline within a few hours, which is why regular activity matters more than occasional intense workouts.
Public health guidelines recommend 150 to 300 minutes of moderate exercise per week for optimal immune function. That works out to roughly 30 minutes of brisk walking, cycling, or swimming five days a week. Extreme endurance training, on the other hand, can temporarily suppress immunity, so the goal is consistency at a moderate level rather than punishing workouts.
Keep Indoor Humidity Between 40% and 60%
The air inside your home and office plays a bigger role in virus transmission than most people appreciate. Research funded by the National Science Foundation found that maintaining indoor relative humidity between 40% and 60% is associated with significantly lower rates of respiratory infections. When humidity drops below 40%, as it often does in heated buildings during winter, viruses survive longer in the air and your nasal passages dry out, reducing their ability to trap and clear pathogens. Above 60%, mold growth becomes a problem.
A simple hygrometer (available for under $15) lets you monitor your indoor humidity. In dry winter months, a humidifier can keep levels in that protective range. This is one of the reasons respiratory illness spikes in winter: it’s not just the cold, it’s the dry indoor air.
Stay Current on Vaccinations
Vaccines remain the most targeted defense against specific infections. For the 2024-2025 flu season, preliminary CDC data shows the influenza vaccine reduced outpatient flu illness by roughly 42% to 56% in adults and 59% to 63% in children, depending on the monitoring network. For preventing flu-related hospitalization, effectiveness ranged from 41% to 57% in adults and reached as high as 78% in children.
Those numbers might not sound like total protection, and they aren’t. But reducing your risk of flu by half, and substantially lowering your chances of ending up in the hospital, is a meaningful benefit from a single annual shot. Vaccinated people who do get sick also tend to have milder, shorter illnesses.
Manage Chronic Stress
Stress that lasts weeks or months does real, measurable damage to immune function. When your body stays in a prolonged stress response, it produces elevated levels of cortisol, a hormone that actively suppresses both your innate and adaptive immune systems. Cortisol reduces the number of active lymphocytes (the white blood cells responsible for targeting specific pathogens) and inhibits the production of signaling molecules your immune cells need to coordinate a defense.
The practical implication: if you’re chronically stressed, you’re more vulnerable to every cold, flu, and respiratory bug you encounter. Strategies that reliably lower cortisol include regular physical activity, adequate sleep, mindfulness practices, and maintaining social connections. These aren’t luxuries. They’re immune support.
Use Masks in High-Risk Situations
During peak cold and flu season, or when respiratory illness is circulating heavily in your community, wearing a mask in crowded indoor spaces offers real protection. N95 respirators filter at least 95% of tiny airborne particles (down to 0.3 micrometers). Standard surgical masks filter between 37% and 69%, a wide range that depends on fit and design. The difference is substantial: a well-fitting N95 provides roughly twice the filtration of most surgical masks.
You don’t need to mask everywhere all the time. But on a packed subway car during flu season, in a hospital waiting room, or while caring for a sick household member, an N95 significantly cuts your exposure.
Try Saline Nasal Rinses
Rinsing your nasal passages with saline solution is a low-cost habit that helps your body clear viruses before they establish an infection. Clinical trials have shown that people who use saline nasal irrigation early during respiratory infections have lower viral loads, faster viral clearance, less frequent fevers, and recover the ability to go about daily activities roughly 1.6 days sooner than those who don’t rinse.
Starting nasal rinses at the first sign of upper respiratory symptoms, ideally at least twice daily, can reduce symptom burden and may even prevent the loss of smell and taste that accompanies some infections. Combining nasal rinses with 60 seconds of gargling isotonic saline can also reduce the amount of infectious virus in saliva. Neti pots and squeeze-bottle rinse kits are widely available at pharmacies.
Consider Probiotics for Respiratory Health
Your gut microbiome influences immune function throughout your body, including your respiratory tract. A Cochrane review of 16 studies found that people taking probiotics were about 24% less likely to develop at least one upper respiratory infection. Among those who took probiotics for three months or longer, the likelihood of getting three or more infections dropped by roughly 41%. People using probiotics were also 42% less likely to need antibiotics for respiratory infections, and their illness episodes were about 1.2 days shorter on average.
Most of the effective regimens in these studies used specific strains of Lactobacillus or similar bacteria at doses of one to one hundred billion colony-forming units per day for at least three months. The evidence is considered low to moderate certainty, meaning probiotics likely help but the size of the benefit may vary. Look for products that specify strain names and CFU counts on the label.
What About Zinc and Vitamin Supplements?
Zinc is widely marketed as a cold-prevention supplement, but the most rigorous evidence is underwhelming. A 2024 Cochrane review of nine studies involving nearly 1,500 participants found that zinc produced little or no reduction in the risk of developing a cold compared to placebo. The results were not statistically significant. Zinc lozenges taken after symptoms start may modestly shorten cold duration, but as a preventive measure, the data doesn’t support routine use.
Vitamin D plays a known role in immune regulation, and people with low vitamin D levels do appear more susceptible to respiratory infections. If you suspect you’re deficient (common in northern latitudes, people with darker skin, and those who spend little time outdoors), getting your levels checked and correcting a deficiency is worthwhile. But for people with adequate vitamin D, supplementing more hasn’t been shown to add extra protection.
Layer Your Defenses
No single habit makes you invincible. The people who get sick least often tend to stack several of these strategies together: consistent sleep, regular moderate exercise, good hand hygiene, up-to-date vaccinations, and managed stress levels. Each one shaves off a portion of your risk, and combined, they create a meaningfully stronger defense. The basics aren’t glamorous, but they work better than any single supplement or gadget on the market.