What Is The Treatment For Heat Rash In A Child?

Hi, My 9 year old son developped a heat rash when we were in Florida over March break. I am often prone to a rash as well after several days straight in the sun. It went away when we got home to the cold and was not an issue until it started to get warmer. Everytime he goes out into the sun, it develops all over his neck (looks like a sunburn) and the tops of his hands. It itches him and causes irritation. It eventually settles down once he is indoors. Is there something I should do to get rid of this or should I be taking him in to his family doctor? Thanks!