Yeast

Yeast: A group of single-celled fungi that reproduce by budding. Although most yeast are harmless (some are used in baking and brewing), other yeast can cause disease in humans. For example, the yeast Candida (once called Monilia) causes thrush (oral infection) and diaper rash in infants, fingernail infections, vaginal area infections after puberty, and a host of problems in patients with immune deficiency.