TEWL

Trans-epidermal water loss is the evaporation of moisture from the skin.

Essential fatty acid deficiency (EFA'S) will eventually lead to prostaglandins (meaning below) formation reduction which results in compromised cell membranes. This is turn contributes to a reduction in lipid phases of the upper epidermis and enhanced TEWL in the skin

Medical Definition of Prostaglandin (extracted from link below)

Prostaglandin: One of a number of hormone-like substances that participate in a wide range of body functions such as the contraction and relaxation of smooth muscle, the dilation and constriction of blood vessels, control of blood pressure, and modulation of inflammation. Prostaglandins are derived from a chemical called arachidonic acid.

https://www.medicinenet.com/script/main/art.asp?articlekey=16461