LIP what you are experiencing is a condition known as prickly heat. it affects many hikers and people involved in many other physical activities. one of the best things that you can possibly do is to keep the area clean and dry. yes i know that that is the obvious answer and that it is often difficult to do. your best bet is to carry a little extra water with you and when you reach a suitable clearing wash the area with water, towel dry and wait a little to let it air dry. I know the Pines arnt the best area to "let it all hang out" but this is a time tested method and is recommended in a few survival handbooks. wash regularly while you are hiking to keep it clean and dry and carry the powder to put on after. that should help.