I wrote a whole page about rashes and remedies, you can find it if you look for the button on the left that reads "Herbal Remedies". Then just scroll down until you find the link about skin rashes. I'm sure you'll find something there to relieve the pain.
Living in West Virginia he really shouldn't be dealing with heat rash year round. It might be possible if you lived in Fl or AZ, but not W. Virgina. I suspect there is something other than heat causing this rash, like allergies. It could be a food allergy or maybe the detergent you're using to wash his clothes. Maybe the bath soap or something toxic he's playing with or medication he's on. There are so many things that can cause a skin reaction.
It might be a good idea to read the section I wrote on allergies. Just look for the button that reads "Allergy Wisdom". Something there might ring a bell. Again, I really don't think you're dealing with heat rash, not when you see it getting sore and he's breaking out year round.