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Factual fiction: Why the cold doesn’t directly get you sick
According to the Centers for Disease Control and Prevention, respiratory illnesses such as colds and the flu are caused by viruses, not by exposure to cold air.
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Naisha Jha - Sat, 03, Jan 2026
- 02:33 EST
- 20
Representative image / Pexels
Myth: Cold weather causes sickness.
Fact: Cold weather weakens the body’s defenses, making it easier for viruses to infect you.
Myth: Going outside with wet hair makes you sick.
Fact: Wet hair can lower body temperature and increase vulnerability to infection, but it does not cause illness on its own.
Every winter, the same warning resurfaces: “Put on a jacket or you’ll get sick.” The idea feels intuitive. Cold weather, runny noses and flu season seem to arrive together. But medically speaking, cold temperatures do not cause illness.
According to the Centers for Disease Control and Prevention, respiratory illnesses such as colds and the flu are caused by viruses, not by exposure to cold air. People get sick when viruses enter the body and the immune system fails to eliminate them, not because they felt cold.
So why do infections spike in winter?
The answer lies in how cold weather affects the body’s first line of defense.
When cold air is inhaled, it lowers the temperature inside the nose and throat. These areas are critical entry points where the immune system first encounters airborne viruses. Researchers at Harvard Medical School have found that colder temperatures weaken immune responses in the nasal passages, reducing the body’s ability to detect and fight viruses early.
Cold air also dries out the mucus lining the airways. Mucus is not just unpleasant; it plays a key protective role by trapping viruses and helping remove them from the body. When the air is dry, mucus becomes thinner and less effective, allowing viruses to linger longer and penetrate deeper into the respiratory system.
In addition, exposure to cold triggers vasoconstriction, the narrowing of blood vessels to conserve heat. While this helps maintain core temperature, it reduces blood flow to the nose and throat. Less blood flow means fewer immune cells reach these tissues, giving viruses more opportunity to multiply once exposure occurs.
This is where prevention matters.
Wearing a jacket does not block viruses, but it helps the body maintain a stable internal temperature so immune defenses can operate effectively. According to the National Institutes of Health, maintaining normal body temperature supports immune function and reduces physiological stress.
Covering the nose and mouth in extreme cold helps protect sensitive airway tissues from dry, cold air. Staying hydrated keeps mucus thick enough to trap pathogens. These steps do not guarantee immunity, but they reduce the conditions that allow infections to take hold, especially during winter when people spend more time indoors and viruses spread more easily.
Cold weather itself does not make people sick. It simply creates an environment that favors infection.
The familiar advice to dress warmly is not superstition; it is biology. By weakening the body’s frontline defenses, cold air gives viruses an advantage once exposure happens.
Staying warm is not about avoiding illness altogether. It is about not making the immune system’s job harder than it already is.
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