The name given to the itchy fungal rash one gets around the groin following a long day in a hot moist environment such as a brewery.
Dawn: "My flange is really itchy!"
Margaret: "Better go see your doctor, it sounds like you have a case of brewer's yeast."
Sam: "This home-brew tastes very sour"
Matt: "It's a special recipe, I use my own brewer's yeast."