When my LO had heat rash, I reduced the temperature water from 38 degrees to 32/33 degrees during shower (this helped a lot!), I wear meshed singlets/short sleeved romper with fan (or ac with thin blanket) instead of sleepsuits/PJs, wipe down a few times during the day to make sure she stays cool. After shower, I only apply Cetaphil baby lotion. So far so good, no more heat rash anymore 😊