Psoriasis is less common in populations whose dietary staples include cold-water fish containing omega-3 fatty acids. But study results have been mixed as to whether fish oil supplements can reduce inflammation and improve psoriasis signs and symptoms, such as itching and scaling. Studies suggest that fish oil delivered by a needle in a vein (intravenously) can decrease the severity of symptoms of some types of psoriasis. But fish oil taken orally doesn't seem to have the same benefit.

Side effects of high-dose fish oil supplements can include a fishy aftertaste, heartburn and nausea. Fish oil affects blood clotting, so if you're taking blood-thinning medication, talk with your doctor before trying it.