Fish liver oil, particularly cod liver oil, has been explored as a supportive therapy for psoriasis due to its high content of omega-3 fatty acids (EPA and DHA) and vitamin D. Scientific interest in fish liver oil for psoriasis is based mainly on the anti-inflammatory effects of these components. Several small clinical trials and observational studies have investigated the effects of omega-3 supplementation on psoriasis severity. Some studies report modest improvements in scaling, redness, and thickness of psoriatic plaques, possibly due to the modulation of inflammatory cytokines and a reduction in leukotriene synthesis. For example, a few randomized controlled trials (RCTs) have shown that high doses of fish oil (often via oral supplementation or intravenous infusion) may provide mild to moderate improvement in symptoms for some patients.

However, the evidence remains limited and inconsistent; other studies have failed to demonstrate a significant benefit over placebo. Meta-analyses generally conclude that while fish oil is safe and might have a small effect, the quality of evidence is low and more robust, large-scale RCTs are needed. Professional dermatology guidelines do not currently recommend fish liver oil as a primary or standalone therapy for psoriasis, though it may be considered as an adjunct. Thus, while there is scientific interest and some preliminary evidence, the overall support is weak (rated 2/5).