Can going outside with wet hair or in cold weather increase the risk of getting a cold or flu?

Cold Weather and Wet Hair Do Not Directly Cause Colds or Flu

Going outside with wet hair or in cold weather does not directly cause colds or flu, as these illnesses are caused exclusively by viral infections transmitted through respiratory droplets and direct contact with contaminated surfaces, not by temperature exposure alone. 1

The Science Behind Respiratory Infections

Viral Transmission is the Only Cause

• Over 200 different viral types cause the common cold, with rhinovirus (30-80%), human coronavirus (15%), respiratory syncytial virus (10-15%), and adenoviruses (5%) being the primary culprits 1
• These viruses spread through airborne droplets when infected persons cough or sneeze, and through direct contact with contaminated objects (utensils, towels, keyboards, toys, telephones) or infectious nasal secretions 1
• Influenza viruses follow similar transmission patterns through respiratory droplets and close contact 1

Why the Myth Persists

• Cold weather theories of disease are culturally ingrained misconceptions that become less prominent with age as people gain better understanding of germ theory 2
• Mexican American and other minority populations show higher adherence to cold weather theories, partially attributable to differences in parent education 2
• The temporal association between winter months and increased respiratory infections creates a false correlation that confuses causation 3

The Cold Weather Paradox: Indirect Effects Only

Cold Exposure May Lower Defenses (But Doesn't Cause Infection)

While cold exposure doesn't cause infection directly, acute cooling of the body surface causes reflex vasoconstriction in the nose and upper airways, which may inhibit respiratory defenses and convert an asymptomatic subclinical viral infection into symptomatic illness 4. However, this requires pre-existing viral infection.

The key distinction: cold exposure may unmask existing infections but cannot create infection without viral exposure. 4

Evidence Against Direct Causation

• Experiments involving inoculation of common cold viruses into the nose combined with periods of cold exposure have failed to demonstrate any effect of cold exposure on susceptibility to infection 4
• Laboratory studies show that brief cold exposure does not support the concept that cold exposure depresses immune function in ways that would increase infection risk 5

Why Winter Has More Infections

The increased winter morbidity and mortality from respiratory infections is attributable to:

• Increased indoor crowding and close contact in heated spaces, which facilitates viral transmission 1
• Closed windows and reduced ventilation increasing indoor viral concentrations 1
• Lower humidity indoors allowing viral particles to remain airborne longer 1
• Behavioral changes reducing outdoor activity and increasing time in confined spaces with infected individuals 3

Practical Guidance for Parents and Patients

What Actually Prevents Colds and Flu

Focus prevention efforts on evidence-based interventions that interrupt viral transmission:

• Hand hygiene is essential - frequent handwashing and avoiding touching eyes, nose, and mouth 1
• Avoid close contact with infected individuals and sharing personal items 1
• Ensure ACIP/AAP-recommended influenza vaccine is administered annually 1
• Stay home when ill to prevent transmission to others 1

What Doesn't Matter for Infection Risk

• Going outside with wet hair 4
• Brief exposure to cold temperatures 5, 4
• Getting "chilled" from weather exposure 4

Important Caveats

Prolonged cold exposure and hypothermia do increase infection risk through different mechanisms (vasoconstriction, immune suppression, increased physiological stress), but this applies to extreme conditions like hypothermia, not routine cold weather exposure 3, 6. This is distinct from the "wet hair" scenario parents worry about.

Cold weather does have legitimate health impacts - including increased blood pressure, cardiovascular stress, and exacerbation of chronic conditions - but these are separate from causing infectious diseases 7.

The Bottom Line for Clinical Practice

Counsel patients that preventing viral transmission through hand hygiene, vaccination, and avoiding close contact with sick individuals is far more effective than avoiding cold weather or wet hair. 1 Redirect parental concern from temperature-based myths toward evidence-based infection control measures that actually reduce disease transmission.