The information provided here is not a replacement for a doctor. You shouldn't use it for the purpose of self-diagnosing or self-medicating but rather so you can have a more informed discussion with a professional TCM practitioner.
In Chinese Medicine heat rash can be treated by one herbs that we have on record. Here is the list below.
Talc might help with heat rash
Why might Talc (Hua Shi) help with heat rash?
Because it is a herb specifically indicated to treat heat rash as can be seen on Talc's page.
Talc is a Cold herb that tastes Sweet. It targets the Bladder and the Stomach.
Its main actions are: Encourages urination. Expels Damp-Heat from the Urinary Bladder. Dispels Summer Heat. Dries Dampness when applied topically.
Other symptoms often associated with heat rash
Urinary tract infection Excessive thirst Restlessness Palpitations Diarrhea Eczema Sores Oliguria Dysuria Fever