What are the possible causes of a yeast related skin rash in an infant? how long does it take to clear up with an ointment & is it contagious?

Part of life: Yeast is around us in the environment & by later infancy at least 5% of the dry weight of poo is yeast. The skin surface is resistant to yeast unless irritated or over hydrated ( like wearing diapers ). The yeast creates a rash when it takes the opportunity of a simple exposure & sets up housekeeping on irritated skin.Improvement with rx occurs within days.