"Put your coat on or you'll catch a cold."

Every parent has said it. Every kid has rolled their eyes at it. But is it actually true? Does being cold really make you sick — or is it just something parents say?

In this episode Daniel finally puts his mom's favorite warning to the test. And the answer turns out to be more interesting than a simple yes or no.

Here's the part that surprises most people. Being cold does NOT make you sick. Not by itself. Colds and the flu are caused by viruses — tiny germs. You can't catch a cold from cold air alone. You can only catch one from an actual virus. Which means, in theory, you could stand outside all winter without a coat and never get sick — as long as there's no virus around.

Daniel declares victory immediately.

But that's not the whole story.

A group of scientists wonde ...