Evening primrose oil (Oenothera biennis), black currant oil (Ribes nigrum), and borage oil (Borago officinalis) are natural sources of a fatty acid called GLA (gamma linolenic acid). Very hard to come by in the diet, GLA is an effective anti-inflammatory agent with none of the side effects of anti-inflammatory drugs. It also promotes healthy growth of skin, hair, and nails. They are frequently suggested for skin conditions (including brittle nails and hair), arthritis, autoimmune disorders, and premenstrual syndrome. Do not expect immediate results; it takes six to eight weeks to see changes after adding GLA to the diet. These three products vary in the amount of GLA they supply and in cost.