Babies:
The babies are at the growing phase, and their skin is sensitive, so they develop the heat rashes more often. Moreover, the sweat glands in the skin of babies are still maturing and are not able to efficiently evaporate the sweat they are producing from the skin. The immature sweat glands in the babies can develop the condition of heat rash in them more frequently as compared to the adults. If the babies get more exposure to heat or warm weather, have an extra layering of clothes, are overdressed, and if they have a fever, then there are more chances of the formation of rashes on the skin.