Going Out With Wet Hair Gives You a Cold
"The warning that leaving the house with wet hair, especially in cold weather, will make you sick."
Colds are caused by viruses, not temperature or dampness, so exposure alone can't cause one. Early 1900s studies on soldiers and Canadian Arctic mounties seemed to support a chill-illness link, but later controlled experiments split volunteers into freezing rooms, some wet and thinly dressed, others bundled and dry, and found both groups caught colds at about the same rate. One real nuance: if a cold virus is already in your system, getting chilled may help symptoms appear sooner, though the chill itself never causes the infection.
Myth vs. FactBeing cold and wet doesn't give you a virus. If you already have one circulating in your body, a chill might nudge symptoms into showing themselves faster.
Sources: Early 1900s military and Arctic studies; modern controlled research discussed via Mayo Clinic.