Go Out With Wet Hair in the Winter and You'll Catch a Cold
How true is the claim? Maybe a bit. Two years ago, scientists divided 180 people into two groups. They chilled one group's feet in cold water, then noted who developed cold symptoms. Those whose feet were dunked were twice as likely to get sick. The theory is that the frigid temperature may have restricted circulation, decreasing germ-fighting immune cells, and that a similar thing could happen with a wet head. Still, this is only one small study, with limited results.
Why it gets repeated: Probably because colds, which are caused by viruses, circulate more in the winter, when people are cooped up and in closer contact, and wet hair seems to be a likely cause.
Bottom line: It's OK to wash and go. Just wash your hands frequently and get vaccinated before the flu season.