“Going outside with wet hair causes a cold.”

• Chilling of the body surface has been associated in at least one controlled study with increased reporting of cold symptoms: Johnson & Eccles (Family Practice, 2005) found that subjects whose feet were immersed in cold water reported significantly more cold symptoms over the following days than controls, suggesting acute chilling may trigger symptoms in people already harboring a virus (this study used cold feet, not wet hair, and did not show new infections were caused).
• Laboratory work has shown that lowering the temperature of the nasal epithelium impairs local innate antiviral defenses (reduced extracellular-vesicle/interferon responses), providing a plausible mechanism by which being cold could make an existing viral exposure more likely to take hold. Evaporative cooling from wet hair could in principle lower head/nasal temperature.
• Colds are genuinely seasonal in temperate climates, and cold, dry conditions favor rhinovirus and other respiratory virus transmission and stability — so cold exposure is correlated (though not causally in the way the folk claim implies) with catching colds.
• Extreme or prolonged chilling causes physiological stress (vasoconstriction, possible transient immune suppression), which is the kernel of truth behind the folk belief.

• A cold is an infectious disease: it requires exposure to one of ~200 respiratory viruses (rhinoviruses most commonly). No virus, no cold — wet hair cannot generate a pathogen. CDC, NHS, Mayo Clinic, Johns Hopkins and MedlinePlus all state colds are caused by viruses spread person-to-person or via contaminated surfaces.
• Classic human-challenge experiments (notably at the UK Common Cold Unit, Salisbury) exposed volunteers to cold, damp conditions — including wet clothing, wet hair and drafts — and found no increase in infection rates compared with controls; chilling did not cause infection in people not exposed to virus.
• Public-health and major medical institutions explicitly list 'going outside with wet hair / cold weather' as a myth: NHS, Mayo Clinic, Cleveland Clinic and Johns Hopkins all note that being cold or wet does not itself cause a cold.
• The seasonal pattern is better explained by indoor crowding, low humidity aiding virus survival and transmission, reduced ventilation, and school terms — not by heat loss from wet hair.
• Even the strongest supporting study (Eccles' cold-feet work) is interpreted by its own authors as possibly converting a pre-existing subclinical infection into symptoms, not as chilling creating a cold; it is small, self-reported, and not replicated for wet hair specifically.
• The claim as written asserts direct causation ('causes a cold'), which no public health agency endorses.

93/100 — the lab’s own confidence in the score above, not a second reading of the claim.

U.S. Centers for Disease Control and Preventiongov · 96 · UK National Health Servicegov · 95 · Mayo Clinicedu · 93 · MedlinePlus, U.S. National Library of Medicinegov · 94 · Johns Hopkins Medicineedu · 92 · Cleveland Clinicedu · 90 · Johnson C, Eccles R., Family Practice (via PubMed)journal · 85 · NIH News in Healthgov · 90

• There is limited indirect evidence that chilling could affect susceptibility after viral exposure: a randomized trial in Family Practice found that participants whose feet were chilled reported more common-cold symptoms over the next several days than controls, but the study did not confirm viral infection and did not test wet hair.
• Laboratory evidence suggests cooler airway temperatures can reduce innate antiviral defenses against rhinovirus and allow more viral replication, which could help explain why cold conditions may influence respiratory infections. This is not evidence that wet hair itself causes colds.
• Wet hair can increase heat loss and make a person feel chilled, so it is biologically plausible that in some circumstances it could contribute slightly to conditions that favor symptoms if a respiratory virus is already present.

• Common colds are caused by respiratory viruses, most often rhinoviruses; wet hair or cold air alone cannot create a cold infection without viral exposure.
• Government medical sources describe colds as spreading through virus-containing droplets, close contact, or contaminated surfaces—not from having wet hair outdoors.
• The strongest support for cold/chilling effects is indirect, inconsistent, or symptom-based; it does not show that going outside with wet hair causes a cold as written.
• A more accurate statement would be: going outside with wet hair may make you cold or uncomfortable, and cold conditions may modestly affect susceptibility, but viruses cause colds.

88/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Centers for Disease Control and Preventiongov · 95 · MedlinePlus / U.S. National Library of Medicinegov · 94 · Family Practice / PubMedjournal · 74 · Proceedings of the National Academy of Sciencesjournal · 87 · Rhinology / PubMedjournal · 72

• While wet hair itself does not cause a cold, exposure to cold environments can cause vasoconstriction (narrowing of blood vessels) in the respiratory tract. Some research suggests this may slightly inhibit local immune responses, potentially allowing a dormant virus already present in the nasal cavity to replicate faster.
• People tend to spend more time indoors in close proximity to others during cold, wet weather, which increases the likelihood of viral transmission and creates a strong seasonal correlation between cold weather and illness.

• The common cold is an infectious viral disease primarily caused by rhinoviruses, adenoviruses, or coronaviruses. It is not caused by environmental factors like temperature or moisture.
• Without the physical presence of a respiratory virus, it is biologically impossible to develop a cold merely by going outside with wet hair or being exposed to freezing temperatures.
• Major medical institutions and public health agencies universally categorize the idea that wet hair or cold weather directly causes a cold as a thoroughly debunked myth.

100/100 — the lab’s own confidence in the score above, not a second reading of the claim.

National Library of Medicine (MedlinePlus)gov · 98 · Mayo Clinicother · 95 · Johns Hopkins Medicineedu · 95

• Cold exposure from wet hair can make someone feel chilled and uncomfortable, but that is not the same as causing a viral cold.[https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-q-and-a-myths-about-catching-a-cold/]
• A review hypothesized that acute cooling might trigger symptoms in someone who already has a subclinical viral infection, although it found no demonstrated effect of cold exposure on susceptibility to infection.[https://pubmed.ncbi.nlm.nih.gov/12357708/]
• A small 2005 study found that participants whose feet were chilled in cold water reported approximately twice as many cold symptoms several days later; this suggests a possible effect on symptom onset, not proof that wet hair causes infection.[https://pubmed.ncbi.nlm.nih.gov/162864４５/]

• The common cold is caused by respiratory viruses, not by wet hair or cold air alone.[https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-q-and-a-myths-about-catching-a-cold/]
• Mayo Clinic states directly that going outside with wet hair does not increase the chance of getting sick.[https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-q-and-a-myths-about-catching-a-cold/]
• Cleveland Clinic likewise says that wet hair cannot make someone sick by itself; a microorganism such as a virus must be involved.[https://health.clevelandclinic.org/can-wet-hair-make-you-sick]
• A peer-reviewed review reports that experiments involving cold-virus inoculation and cold exposure failed to show increased susceptibility to infection, while noting that chilling might theoretically affect symptoms in someone already infected.[https://pubmed.ncbi.nlm.nih.gov/12357708/]
• A 2023 medical review states that laboratory experiments have failed to demonstrate an effect of chilling on susceptibility to common-cold infection.[https://pmc.ncbi.nlm.nih.gov/articles/PMC10324571/]

95/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Mayo Clinicother · 95 · Cleveland Clinicother · 92 · PubMed; review article indexed by the U.S. National Library of Medicinejournal · 94 · Peer-reviewed review article hosted by PubMed Centraljournal · 90

• Some lab studies show cooler nasal temperatures can weaken local innate antiviral defenses, allowing rhinoviruses to replicate more readily if already present.
• Colds peak in colder months, creating a perceived link with going outside while wet or chilled.
• Anecdotes and a few older chilling experiments have been interpreted as mild immune or circulatory effects that could raise susceptibility after viral exposure.

• Colds are caused by viruses (mainly rhinoviruses), not by wet hair, cold air, or being chilled; infection requires exposure to the virus.
• Major health authorities state that getting wet or cold does not cause a cold.
• Human challenge studies (including historic Common Cold Unit work) did not find that chilling or similar exposure produces colds without the virus.
• No clinical evidence specifically shows that going outside with wet hair causes colds.

84/100 — the lab’s own confidence in the score above, not a second reading of the claim.

Mayo Clinicother · 95 · NHSgov · 95 · PNASjournal · 92 · MedlinePlus (NIH)gov · 94