Brewer's yeast is a kind of yeast that is a by-product of brewing beer. Dietary supplements containing brewer's yeast often contain non-living, dried yeast. People use brewer’s yeast to make medicine. Brewer's yeast is used for diarrhea, the common cold and other upper respiratory tract infections, influenza, swine flu, loss of appetite, acne, premenstrual syndrome (PMS), recurring boils on the skin (furunculosis), and type 2 diabetes. It has also been used as a source of B vitamins, chromium, and protein.