You're speaking with Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply.
I regret that we're not allowed to communicate by private email. Please stay in this conversation. We don't recognize prickly heat rash in dogs. We do see a truncal solar dermatitis - usually on the flanks and abdominal skin while the nose and ears are the areas most exposed and thus most susceptible to actinic (pre-cancerous) damage. Can you upload a photo(s) of representative skin to our conversation? You can use the paperclip icon in the toolbar above your message box (if you can see that icon) or you can use an external app such as dropbox.com/ i can be more accurate for you if I can see what you're seeing.