METHODS: Eicosapentaenoic acid (EPA), abundant in oily fish, is reported to reduce skin inflammation and provide photoprotection, potential mechanisms include competition with arachidonic acid (AA) for metabolism by cyclooxygenases/lipoxygenases to less pro-inflammatory mediators. We thus examine impact of EPA intake on levels of AA, EPA and their resulting eicosanoids in human skin with or without ultraviolet radiation (UVR) challenge.
RESULTS: In a double-blind randomised controlled study, 79 females took 5 g EPA-rich or control lipid for 12 wk. Pre- and post-supplementation, red blood cell and skin polyunsaturated fatty acids were assessed by GC, and eicosanoids from unexposed and UVR-exposed skin by LC-MS/MS. Active supplementation increased red blood cell and dermal EPA versus control (both p < 0.001), lowering relative AA:EPA content (4:1 versus 15:1 and 5:1 versus 11:1, respectively; both p < 0.001). Pre-supplementation, UVR increased PGE2, 12-hydroxyeicosatetraenoic acids, 12-HEPE (all p < 0.001) and PGE3 (p < 0.05). Post-EPA, PGE2 was reduced in unchallenged skin (p < 0.05) while EPA-derived PGE3 (non-sign) and 12-HEPE (p < 0.01) were elevated post-UVR. Thus, post-EPA, PGE2 :PGE3 was lower in unchallenged (12:1 versus 28:1; p < 0.05) and UVR exposed (12:1 versus 54:1; p < 0.01) skin; 12-hydroxyeicosatetraenoic acids:12-HEPE was lower in UVR-exposed skin (3:1 versus 11:1; p < 0.001).
CONCLUSIONS: Dietary EPA augments skin EPA:AA content, shifting eicosanoid synthesis towards less pro-inflammatory species, and promoting a regulatory milieu under basal conditions and in response to inflammatory insult.

OBJECTIVE: The erythema resulting from the minimal erythema dose (MED) test is subjectively assessed. The evaluator visually grades erythema on an ordinal scale. Both intra- and interobserver variation have been found for this erythema assessment. We wanted to examine if objective measurements could be used to confirm the subjective finding.
METHODS: One hundred two ultraviolet radiation (UVR)-exposed skin sites on the backs of 17 healthy volunteers were assessed. Erythema was visually graded according to a 5-point scale [0, (+), 1+, 2+, 3+] and objectively measured by a skin reflectance meter. Skin water content was objectively measured by tissue dielectric constant measurements.
RESULTS: The relationship between subjective assessments and objective measurements of erythema was found to be linear (R(2)  = 0.482, P < 0.0001). A positive correlation was found between subjective assessments of erythema and objective measurements of water content (Spearman\'s Rho = 0.414, P < 0.0001). Water content in categories 2+ and 3+ of the subjective erythema assessments differed significantly from the lesser categories (P < 0.0001). A linear relationship was found between the objective measurements of erythema and water content (R(2)  = 0.241, P < 0.0001).
CONCLUSIONS: Objective measurements of skin erythema and water content after UV exposure were in good agreement with the subjective assessments of erythema, but showed considerable interpersonal variation.