Could be just dry lips from the sun and wind. Try Chapstick in any of the many brands and flavors available on the market. However if it persists it could be what is called "Sun Posining" and you will want to take him to the doctor. Try the chapstick and watch him closely for a couple of days. If it doesn't get worse or goes away then it's just dry lips from the sun and wind. Sun posin will get much worse and will break out in scabs. It will start on the lips sometimes but can start on anywhere on the body and will look like a very severe burn after a couple of days. I saw a lot of guys get it when I was in Vietnam and the main cure is get out of the sun. Some people just can't take the sun. But more than likely what your son has is a case of dry lips.

If it starts getting worse go see your doctor immediately. It doesn't normally leave any bad scars.

Frogman.