A listener from Ontario, California wrote to A Moment of Science with a question her sons had asked her.
The boys wondered why is it that when you get sunburned you often feel chilled. It really does seem like a contradiction: you've been burned, but you feel cold.
The answer to this seeming contradiction is in your blood.
Sunburn is an injury to your skin, and your body's usual reaction to being injured is to enlarge the blood vessels in the damaged area. This allows more blood to be circulated near the injury, where it can deliver cells to help heal the wound.
Damage to the skin
Since sunburn is usually damage to the surface of your skin, the blood vessels in the area of the burned skin enlarge so that more blood is circulated there; this is where the redness comes from.
When you're sunburned a large area of your body is usually involved, so a result of so much blood being near the surface of your skin is that you lose more than a normal amount of body heat through it.
Activating reactions
Your brain tries to balance this loss of heat by activating reactions which attempt to conserve heat. A common reaction is shivering, which is the body trying to generate heat in an effort to compensate for the heat that is being lost.
So, even while your skin feels hot to the touch, you shiver and feel chilled as your body tries to make up for the extra heat loss.