What types of seafood can cause allergies?

Allergies occur when your body reacts to specific proteins in foods. Allergic reactions can be caused by different types of seafood.

Fish (seafood with a backbone) that can cause allergic reactions include:

• salmon
• cod
• mackerel
• sardines
• herring
• tuna
• eels

Shellfish (seafood without a backbone) can also cause allergic reactions, and include:

• crustaceans such as prawns / shrimp, lobster, crab, crayfish, yabbies
• molluscs such as oysters, mussels, clams, octopus, squid, calamari, abalone, sea slugs, eels

Some people are allergic to fish only, others to shellfish only, and others to both groups of seafood.

Around 4 out of 5 people with seafood allergy will have the allergy for life. If you are allergic to one type of seafood, you can't predict whether you'll be allergic to any other type of seafood. The only way to find out is through allergy testing or experience.

What are the symptoms of seafood allergy?

Most people who are allergic to seafood have mild symptoms such as:

• hives
• tingling in the mouth
• some swelling in the face, lips or eyes
• abdominal (stomach) pain, vomiting or diarrhoea

But some people experience dangerous symptoms of anaphylaxis such as:

• difficulty breathing
• swelling of the tongue or tightness in the throat
• hoarse voice, wheezing or difficulty talking
• dizziness or collapse due to a sudden drop in blood pressure

If you are allergic to seafood, symptoms usually appear within minutes, but some people (especially those with an allergy to oysters, abalone, squid or prawns) may not experience symptoms until hours later. This reaction sometimes happens after exercise.

How is seafood allergy diagnosed?

Seafood allergy is diagnosed with allergy testing, done under medical supervision. This is the only way to diagnose your specific seafood allergy. If you suspect you have an allergy, see your doctor. Your doctor can refer you for skin or blood tests, and help you understand what your test results mean.

Seafood allergies are complex. Even among fish, there are different groups of fish, and if you are allergic to one group of fish, you may be able to safely eat fish from other groups.

Avoid testing methods advertised online or in print media. Tests that are considered unreliable include hair analysis, Alcat or Vega tests, kinesiology, iridology, reflexology, pulse and cytotoxic food tests.

How is seafood allergy treated?

There aren't currently any treatments routinely used to cure food allergies, including seafood allergy.

The best way to avoid experiencing symptoms of seafood allergy is to avoid contact with seafood.

If your doctor diagnoses a seafood allergy, they may also prescribe an adrenaline auto-injector, such as EpiPen or Anapen. If you are prescribed an adrenaline auto-injector, it's important to always keep it with you to treat a reaction if you are accidentally exposed to seafood.

How can I avoid seafood?

It's easy to avoid cooking or buying seafood, but ingredients made from seafood are added to many foods that you might not expect. Check the labels on processed or packaged foods.

Canned fish or shellfish are obvious sources of seafood. Other products and menu items to watch out for include:

• sauces, such as oyster sauce, fish sauce or marinara sauce
• fish paste or fish stock
• prawn crackers and prawn crisps
• sushi
• Caesar salad (which may include anchovies)
• pizza (which may come with anchovies or other seafood)
• cooking oil previously used to cook fish

If you order a stir-fried dish or meat curry in a restaurant, for example, it may have been cooked with fish sauce. Make it very clear to waiters that you have a genuine allergy and your meal must not contain any seafood, fish sauce or oyster sauce.

Fish oil supplements are unlikely to cause an adverse reaction, but it's best to avoid them. Speak with your doctor if you have concerns about your nutrition — they can also refer you to a dietitian for advice.

Glucosamine supplements (sometimes used for osteoarthritis) are made from the shells of crustaceans and are not suitable if you are allergic to shellfish.

Isinglass is an additive used to stop beer and wine from going cloudy. It is made from the bladders of fish, but food authorities consider it is so unlikely to cause an allergic reaction that legally it doesn't need to be included on the label.

A small number of people are so sensitive to any kind of fish that they can have a reaction to the steam produced when fish is being cooked. This is more likely in children who also have asthma.

Resources and support

To learn more about the symptoms, diagnosis, and management of seafood allergy, see the Sydney Childrens Hospitals Network fact sheet.

Read more on food allergies such as seafood allergy on the Australasian Society of Clinical Immunology and Allergy (ASCIA) website.