Heat rash, also known as prickly heat or summer rash, is an eruption of little bumps (and sometimes tiny blisters) on the skin that can show up when your baby overheats. (babycenter.com)
Just like prickly heat, this type of heat rash occurs when the sweat ducts become blocked and rupture. (verywell.com)
In areas of extreme heat and humidity, the ducts of sweat glands may get clogged and inflamed; resulting in prickly heat rash that is characterized by very small bumps or rashes that may appear solitary or clustered. (newkidscenter.com)