There are two main families of PUFAs: n-3 and n-6 PUFAs. Alpha-linolenic acid (ALA) is the only essential n-3 PUFA, while linoleic acid is the only essential n-6 PUFA. These fatty acids form the building blocks for downstream long-chain fatty acids: On the n-6 side, linoleic acid converts to gamma-linolenic acid (GLA) and dihomo-gamma-linolenic acid (DGLA), the latter of which may be converted to either pro-inflammatory arachidonic acid (AA) or anti-inflammatory prostaglandins, prostaglandin E1 (PGE1). AA (which can also be derived from the diet) is primarily a precursor to pro-inflammatory eicosanoids, prostaglandin E2 (PGE2), and leukotrienes and, to a much smaller extent, anti-inflammatory prostacyclin. On the n-3 side, a small amount of ALA converts to eicosapentaenoic acid (EPA), and then to docosahexaenoic acid (DHA). EPA serves primarily as a precursor to anti-inflammatory prostaglandins, prostaglandin E3 (PGE3) and inhibits both the production of AA from DGLA and the production of PGE2 or thromboxane from AA. Skin cells produce eicosanoids in response to various stimuli contributing to inflammatory conditions.The active involvement of fatty acids in skin health and epidermal barrier function justifies the choice of systemic supplementation with n-3PUFA as an effective strategy for the improvement of inflammatory conditions. Epidemiological observations of a lower incidence of autoimmune and inflammatory disorders, including psoriasis, in a population of Greenland Eskimos compared with gender- and age-matched groups living in Denmark provided early suggestive evidence of the important role of n-3 PUFAs dietary intake on inflammation. An improvement in psoriasis has also been observed during daily dietary supplementation with fish oil containing n-3 PUFAs. As mentioned, AA is a pro-inflammatory fatty acid. As a result, a low dietary intake of AA, typical of low-protein and vegetarian diets, may produce a less anti-inflammatory effects. The Western diet is "deficient" in n-3 PUFAs, with an n-6/n-3 ratio of 15/1 to 16/1, as compared to the 1/1 ratio as found in wild animals and presumably human beings prior to the industrial revolution. Although the ability of a low-protein diet to improve symptoms in psoriasis patients has not been consistently supported a remarkable treatment efficacy was reported for a patient by Schamberg. In a case-control study, Naldi et al showed that an increased intake of fresh fruits and certain vegetables was linked to a decreased prevalence of psoriasis, although the mechanism was not clear.