Fish allergies are the result of your body's misidentification of certain proteins in fish. Instead of recognizing them as harmless, your immune system thinks that fish proteins are dangerous and sends out the antibody immunoglobulin E to get rid of the invading allergens. The antibody then triggers chemicals to fight off the allergen. These chemicals are what cause allergic symptoms. Once you have one allergic reaction to fish, you'll always have an allergic reaction to fish. Such allergies tend to be life-long.
Omega-3 fatty acids are fatty acids that naturally occur in many types of fish; they're suspected to lower triglycerides, reduce the risk of heart attack and generally increase heart health. However, if you're allergic to fish, you're advised to stay away from the fish that contain omega-3 (like salmon, mackerel, sardines and herring) and from omega-3 products that come from fish. While the allergenic fish proteins that cause reactions are normally found in the flesh of fish, traces of those proteins can be found in omega-3 extracts, as well. But luckily, omega-3 is found in other sources besides fish; these sources won't trigger fish allergies. Flaxseed, walnuts, special enriched eggs and the green leafy purslane all contain omega-3 and can be added to your diet for a source of the healthful fatty acids. There are also algae sources for omega-3 supplements.
However, some people may react to omega-3, regardless of whether they have any allergies. Side effects that might accompany the intake of omega-3 fatty acids are often related to increased bleeding. The higher the intake of omega-3, the more likely the bleeding will be significant. With large amounts of omega-3, you may suffer nosebleeds or blood in your urine. Some studies have shown that omega-3 fatty acids can cause a slight drop in blood pressure, too.