How do you prevent heat rash from occurring?

How do you prevent heat rash from occurring?
I get a heat rash on my hairline and chest after running/working out. I always shower afterwards, but it doesn’t keep this horrible heat rash from breaking out in those areas. *I’ve already tried hydrocortizone, acne creams, masks, soaps, nothing, everything, loose clothes, etc. Maybe BABY RASH CREAM??? Any suggestions?

I swear by Vitamin A&D oitment, although it smells horrible.

Also try sprinkling some powder for prickly heat onto towel & dab on forehead & chest prior to working out & re-apply after shower.