Fish oil contains omega-3 fatty acids. These essential fatty acids (EFAs) have been scientifically shown to be helpful for allergies, arthritis, skin problems, heart, kidneys and more. Dogs can’t make these fatty acids on their own, so they must come from the diet. There are two types of omega-3s: docosahexaenoic acid (DHA) to support brain function and eicosapentaenoic acid (EPA) to reduce inflammation.