Nystatin, sold under the brandname Mycostatin among others, is an antifungal medication. It is used to treat Candida infections of the skin including diaper rash, thrush, esophageal candidiasis, and vaginal yeast infections. It may also be used to prevent candidiasis in those who are at high risk. Nystatin may be used by mouth, in the vagina, or applied to the skin. Common side effects when applied to the skin include burning, itching, and a rash. Common side effects when taken by mouth include vomiting and diarrhea. During pregnancy use in the vagina is safe while other formulations have not been studied in this group. It works by disrupting the cell membrane of the fungal cells. Nystatin was discovered in 1950 by Rachel Fuller Brown and Elizabeth Lee Hazen. It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system. It is available as a generic medication. The wholesale price of the cream in the developing world is about 0.70 USD per 30 gram tube. In the United States it is less than 25 USD for a course of treatment. It is made from the bacterium, Streptomyces noursei.