You're heading out the door for a day of fun in the sun with your family.

You grab the sunscreen because you know a sun protection factor, or SPF, of 30 is going to protect your exposed skin from getting burned.

But most people don't know that skin covered by clothing can still get sunburned.

"Natural clothing without sun protective factors will have an SPF of approximately 1 to 4, based on how tight the weave is and how breathable the material is. So it actually does not give you that much sun protection."

But Dr. Dawn Davis, a Mayo Clinic dermatologist, says there are special types of clothing that will protect you.

The clothing industry has now allowed the integration of a weave of microfibers into certain clothes that allow it to have a UPF, or ultraviolet protection factor, that's equivalent to SPF of sunscreen.

She says UPF is even calculated the same way SPF is.

"You can spend 50 minutes outdoors with a piece of clothing before developing mild redness versus 10 minutes without, you would have a protective factor of 50 over 10, which is a UPF of 5."

For the Mayo Clinic News Network, I'm Ian Roth.