Heat rash...Help!!

Kendra
My poor baby boy gets the worst heat rash. What can I do to help this? I try not to go out in the heat too much, but I have a 4 year old at home as well that I feel terrible keeping cooped up in the house. It looks so painful. Help! 
*****Update*****
It turns out that this was not heat rash (or baby acne like the doctor kept trying to tell me). He has cradle cap on his face, ears, upper back, and upper chest. How does this happen?!