yeast

yeast A group of single-celled fungi that reproduce by budding. Most yeast is harmless, and yeast is commonly present without ill effect on normal human skin and mucous membranes, including the gastrointestinal (GI) tract. In the GI tract, the amount of yeast is usually controlled by helpful bacteria, although this balance can be upset by illness, immune system problems, or antibiotic use. Extreme overproliferation of yeast can cause discomfort and disease. For example, the common yeast Candida albicans (once called Monilia) causes thrush and rashes, fingernail infections, vaginal infections, and a host of other problems in patients with immune deficiency. See also Candida albicans; candidiasis; thrush; yeast infection; yeast rash.