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.
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.
Urinary tract infection Excessive thirst Restlessness Palpitations Diarrhea Eczema Sores Oliguria Dysuria Fever