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If you have an allergy to fish or shellfish, you may want to avoid eating fish oil as well. Fish and shellfish allergies can cause serious life-threatening reactions, as can fish oil.

A fish allergy is a common food allergy. Up to about 2.3 percent of people in the United States are allergic to fish. A protein in fish muscle called parvalbumin may trigger a reaction in some people, and there is a chance this protein may be found in some fish oils as well.

While allergic reactions to fish oil are extremely rare, they have been reported.

If you have a fish or shellfish allergy, the American College of Allergy, Asthma & Immunology (ACAAI) recommends that you visit a dermatologist, bring the fish oil supplements you are considering taking, and get tested to see if you have a reaction to those specific supplements.

According to the ACAAI, people who are allergic to fish and shellfish have a low risk of having an allergic reaction from pure fish oil.

A small 2008 study tested six people with fish allergies. It found that fish oil supplements did not cause a reaction. However, the study is old, and in addition to the small number of people tested, the study only included two brands of fish oil supplements.

Newer, larger studies are needed to determine definitively if fish oil can cause allergies.

An allergic reaction to fish oil is a reaction to fish or shellfish. About 40 percent of people with fish or shellfish allergies have their first allergic reaction as an adult. These food allergies can begin in childhood and last for life.

symptoms of fish oil allergy
  • nasal congestion
  • wheezing
  • headaches
  • itching
  • hives or rash
  • nausea or vomiting
  • swelling of the lips, tongue, face
  • swelling of the hands or other parts of the body
  • stomach pain or diarrhea

Symptoms of a fish oil allergy will be the same as a fish or shellfish allergy. You may have a serious reaction called anaphylaxis. This can be life-threatening.

Seek emergency care for these symptoms
  • swelling in throat
  • a lump in the throat
  • difficulty breathing
  • dizziness or fainting
  • very low blood pressure
  • shock

See your family doctor or allergist if you have any symptoms of an allergic reaction after taking fish oil. Keep a food diary to track symptoms. Record when and how much fish oil you took, what you ate, and any symptoms.

An allergist — a doctor who specializes in allergies — can diagnose your fish oil, fish, or shellfish allergy. You may need one or more tests, such as:

  • Blood test. Your doctor will take a blood sample with a needle. The blood is sent to a lab to test for antibodies that your body makes if you are allergic to fish or shellfish.
  • Skin-prick test. A tiny amount of protein from fish or shellfish is placed on a needle. Your doctor will gently scratch or prick the skin on your arm with the needle. If you get a skin reaction like a raised or red spot within 15 to 20 minutes, you may be allergic.
  • Food challenge test. Your doctor will give you a small amount of fish or shellfish to eat in the clinic. If you have any reaction, you can be diagnosed and treated immediately.

Fish oil is oil or fat from fish tissue. It commonly comes from oily fish like anchovies, mackerel, herring, and tuna. It can also be made from the livers of other fish like cod.

Other names for fish oil

If you have an allergic reaction to fish oil, you may need to avoid these oils as well since they are all types of fish oil.

  • cod liver oil
  • krill oil
  • marine lipid oil
  • tuna oil
  • salmon oil

Even pure fish oil may have tiny amounts of fish or shellfish proteins. This happens because fish oil supplements are not regulated or tested. They may be made in the same factories as other types of seafood products.

Fish oil capsules may also contain fish gelatin. For this reason, many fish oil supplements are labeled with the warning, “Avoid this product if you are allergic to fish.”

Fish oil is also used in a prescription drug to treat high blood cholesterol levels. For example, Lovaza is a medication made from several kinds of fish oil. Drug reviews advise that people who are allergic or sensitive to fish or shellfish may have side effects from Lovaza.

If you do not have a fish or shellfish allergy you’ll likely not have a reaction to fish oil. Some people may have side effects to fish oil. This does not mean you have an allergy.

You may be sensitive to fish oil. Taking too much fish oil can also be harmful. Tell your doctor if you have any of these symptoms after taking fish oil.

Side effects of fish oil
  • nausea
  • acid reflux
  • upset stomach
  • bloating
  • diarrhea
  • low blood pressure
  • bleeding gums
  • insomnia

If you discover you do have a fish oil allergy or sensitivity, you may need to avoid certain foods. Some foods have added fish oil. Food manufacturers may add fish oil to packaged foods to help preserve them. Fish oil may also be used to add health benefits to some foods.

Check labels carefully. Foods that are labeled “enriched” or “fortified” may have added fish oils.

Foods that may contain added fish oil
  • salad dressings
  • sauces
  • boxed soups
  • soup mixes
  • yogurt
  • frozen dinners
  • protein shakes
  • omega-3 oil
  • multivitamins

Fish oil is a recommended health supplement because it is high in omega-3 fatty acids. These fats are good for your heart and overall health. You can still get omega-3 fatty acids from other foods.

Shop for vegan or fish-free omega-3.

other sources for omega-3
  • chia seeds
  • flaxseeds
  • soybeans
  • walnuts
  • hemp seeds
  • Brussels sprouts
  • purslane
  • spinach
  • pastured eggs
  • enriched eggs
  • grass-fed dairy products
  • grass-fed beef
  • vegan supplements

A fish oil allergy is very rare and is actually an allergic reaction to protein from fish or shellfish. You can have side effects from fish oil without having an allergy.

Symptoms of fish oil allergy are the same as a fish or shellfish allergy. Your doctor can give you several tests that help to confirm if you have an allergy to fish oil.

If you do have fish oil allergy, do not take fish oil supplements and keep an epinephrine pen with you at all times.