Evening primrose, also known as Oenothera biennis, is a plant with many synonyms. Some of these include: sundrop, night willow-herb, fever plant, and king's cure-all. The yellow flowers of this plant open in the evening, hence its common name. Evening primrose has been traditionally used for medicinal purposes, and its oil is used in many skin care products. In addition, evening primrose has been found to be effective in treating eczema, premenstrual syndrome, hot flashes, and breast pain. With numerous benefits and many different names, evening primrose is a versatile and valuable plant.