We have to be complete. This can vary by clinical expertise, presentation, follow up, and the history but in general it's very difficult to ID a rash on history and physical alone. You'll miss a lot of viral and bacterial based rashes and the occasional "other" rash by just assuming yeast and treatment can heavily vary. Don't want to give strong steroids if it's bacterial or fungal as that can lessen the immune response and worsen the rash. Don't want to give fungal treatment if it's one of the other types as that can delay care, etc. I'll often give the anti perspirant type of relief inpatient right away it's a high index of suspicion for fungal but still confirm with KOH, sometimes wood lamp. That's all super cheap with little risk