Essential fatty acid deficiency usually occurs if hyperalimentation is extended for more than 1 month and when soybean oil is not administered at least twice a week. There is a decrease in linolenic, linoleic, and arachidonic acids and an increase in oleic and palmitoleic acid. In addition to the skin changes, there may be poor wound healing, increased susceptibility to infection, lethargy, and thrombocytopenia. It is characterized by a triene-to-tetraene ratio >0.4.