Oenothera biennis, commonly known as evening primrose, is a flowering plant that is native to North America. Indigenous tribes have been using this plant as a medicinal crop for hundreds of years, treating ailments such as bruises, hemorrhoids, digestive problems, and sore throats. Evening primrose oil is currently used in skin care products due to its high content of gamma-linolenic acid (GLA).

The human body can produce GLA from linoleic acid, an essential fatty acid that must be obtained from dietary sources. After ingesting linoleic acid, the enzyme Delta-6-Desaturase (D6D) converts it into GLA. GLA is then converted into a very important compound called Prostaglandin 1, a key molecule for maintaining healthy skin. Those with skin disorders such as eczema and psoriasis often have reduced activity of the D6D enzyme, which means they cannot effectively convert linoleic acid to GLA. Therefore, the use of evening primrose oil is very beneficial for those with inflammatory skin disorders since it contains such a high percentage of GLA.