Cold and flu season often brings the wise advice: wash your hands, drink water, and try not to get sick.
But why do these habits matter?
Viruses can spread through the air.
When we breathe, talk, cough, or sneeze, we release tiny particles into the air. Some of these particles are very small and can carry respiratory viruses.
Research has shown that people release these particles even during normal breathing. It has also shown that some people release more particles than others.¹
This helps explain why respiratory viruses can spread even when someone is not coughing or sneezing nearby.
Your airways have their own cleaning system.
The inside of your nose and airways is covered with a thin layer of mucus. This mucus helps trap dust, germs, and other particles.
Tiny hair-like structures called cilia move the mucus along so your body can clear it out. For this system to work well, the surface of the airways needs enough moisture.²
Dry air may make this process harder. In one animal study, low humidity slowed mucus clearance and weakened some of the body’s defenses against influenza.³
That does
not
mean drinking extra water alone will prevent the flu or another respiratory virus.
Staying normally hydrated is still important, especially when you are sick. But the stronger scientific finding is that moisture in the airways and the surrounding air can affect how well our natural defenses work.
Handwashing still helps.
Many respiratory viruses can spread through the air, but handwashing is still useful.
A large review of 26 studies found that programs that encouraged handwashing with soap were linked with fewer respiratory infections overall.⁴
So the basics still matter.
Stay normally hydrated. Avoid very dry indoor air when you can. Wash your hands with soap and water.
None of these habits can guarantee that you will not get sick. But they can help support the systems your body already uses to protect you.
Sources
Edwards DA, Man JC, Brand P, et al. “Inhaling to mitigate exhaled bioaerosols.” Proceedings of the National Academy of Sciences. 2004;101(50):17383–17388.
https://pubmed.ncbi.nlm.nih.gov/15583121/
Button B, Anderson WH, Boucher RC. Research on airway-surface hydration, mucus, and mucociliary clearance. Physiological Reviews.
https://journals.physiology.org/doi/10.1152/physrev.00004.2021
Kudo E, Song E, Yockey LJ, et al. “Low ambient humidity impairs barrier function and innate resistance against influenza infection.” Proceedings of the National Academy of Sciences. 2019;116(22):10905–10910.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6561219/
Ross I, Bick S, Ayieko P, et al. “Effectiveness of handwashing with soap for preventing acute respiratory infections in low-income and middle-income countries: a systematic review and meta-analysis.” The Lancet. 2023;401(10389):1681–1690.
https://pubmed.ncbi.nlm.nih.gov/37121242/
