The belief that getting soaked in the rain or experiencing a chill directly causes a common cold is a widespread misconception. Exposure to rain or cold weather alone cannot make a person sick, as a cold requires a specific infectious agent to take hold. Current biological understanding confirms that respiratory illnesses begin only through viral transmission.
The Viral Origin of the Common Cold
The common cold is caused exclusively by viruses, which must be transmitted from person to person for infection to occur. Rhinoviruses are the most frequent culprits, though over 200 different virus types can cause the familiar symptoms. These microscopic viral particles must enter the respiratory tract and hijack cells to replicate, a process that rain or cold air cannot initiate.
Viruses spread through respiratory droplets released when an infected person coughs, sneezes, or talks. They can also survive on surfaces for hours, waiting to be picked up by unwashed hands and transferred to the eyes, nose, or mouth. The seasonality of colds coincides with times when these viruses are most active and transmission is highest. The presence of a virus, not the outside temperature, is the definitive requirement for developing a cold.
The Connection Between Cold Temperatures and Susceptibility
While cold air does not cause a cold, it can create biological conditions that make a person more susceptible to an existing virus. Research indicates that a drop in temperature in the nasal passages impairs the body’s local immune response. When nasal tissue temperature drops by just 5 degrees Celsius, the immune system’s ability to fight off pathogens in that area is reduced.
This temperature drop affects the production and function of extracellular vesicles (EVs), which are tiny sacs released by nasal cells to trap and expel viruses. The number of these protective EVs can decrease by over 40% in colder temperatures, compromising the first line of defense. Colder conditions also reduce the effectiveness of virus-fighting proteins like interferon, which block viral replication. This allows a virus already present in the nose a greater opportunity to multiply and establish a full infection.
Another factor linking cold weather to illness is the resulting change in human behavior. As temperatures drop, people spend more time indoors in close proximity to one another. This increased density facilitates the efficient transmission of respiratory viruses between individuals. The combination of a compromised local immune response and increased viral exposure explains why the cold season sees a spike in common cold cases.
Stopping the Spread of Cold Viruses
Since colds are spread by viruses, prevention must focus on interrupting transmission routes. The most effective strategy involves practicing rigorous hand hygiene throughout the day. Hands should be washed with soap and water for a minimum of 20 seconds, especially after being in public or before eating.
If soap and water are not readily available, use an alcohol-based hand sanitizer containing at least 60% alcohol. Individuals should also consciously avoid touching their face, including the eyes, nose, and mouth, as these are the primary entry points for respiratory viruses.
To prevent spreading the virus, infected individuals should cough or sneeze into a tissue and dispose of it immediately, or use their elbow if a tissue is unavailable. High-touch surfaces in shared environments should be routinely cleaned and disinfected. Individuals who are feeling sick should stay home to reduce the chances of passing the virus to others.