What causes sudden shellfish allergy

What causes sudden shellfish allergy

Types of seafood that can cause allergies

Allergic reactions can be caused by:

  1. fish, either unused or canned
  2. shellfish such as prawns (sometimes called shrimp), crab, yabbies, lobster, crayfish, bugs (often called Balmain or Moreton Bay bugs) and marron
  3. molluscs such as oysters, mussels, scallops, pipis, clams, octopus, squid, calamari and abalone
  4. eels

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 discover out is through testing or experience.

How to avoid seafood

It’s simple to avoid cooking or buying seafood, but ingredients made from seafood are added to numerous foods that you might not expect.

Check the labels on processed or packaged foods.

What causes sudden shellfish allergy

Canned fish or shellfish are obviously sources of seafood; other products and menu items to watch out for include:

  1. sauces such as oyster sauce and fish sauce (used in numerous Asian dishes)
  2. prawn crackers and prawn crisps
  3. pizza (which may come with anchovies or other seafood)
  4. fish paste
  5. cooking oil previously used to cook fish
  6. fish stock
  7. marinara sauce (used on pasta or pizza)
  8. sushi
  9. Caesar salad (which may include anchovies)
  10. fish or krill oil supplements

If you order a stir-fried dish or meat curry in a restaurant, for example, it may own been cooked with fish sauce.

Make it extremely clear to waiters that you own 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 probably safest to avoid them.

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.

What causes sudden shellfish allergy

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


ASCIA(Allergic and toxic reactions to seafood), Sydney Children’s Hospital Network(Allergy – seafood allergy (includes every fish and seafood)), Australian Government(IFN 08-17 Mandatory allergen labelling), Australian Family Physician(Your questions about complementary medicines answered: glucosamine)

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: April 2018

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The symptoms of a food allergy almost always develop a few seconds or minutes after eating the food.

Some people may develop a severe allergic reaction (anaphylaxis), which can be life threatening.

The most common type of allergic reaction to food is known as an IgE-mediated food allergy.

Symptoms include:

  1. tingling or itching in the mouth
  2. wheezing or shortness of breath
  3. feeling ill (nausea) or vomiting
  4. a raised, itchy red rash (hives) – in some cases, the skin can turn red and itchy, but without a raised rash
  5. abdominal pain or diarrhoea
  6. difficulty swallowing
  7. swelling of the face, mouth (angioedema), throat or other areas of the body
  8. feeling dizzy and lightheaded
  9. hay fever-like symptoms, such as sneezing or itchy eyes (allergic conjunctivitis)

Non-IgE-mediated food allergy

Another type of allergic reaction is a non-IgE-mediated food allergy.

What causes sudden shellfish allergy

The symptoms of this type of allergy can take much longer to develop – sometimes up to several days.

Some symptoms of a non IgE-mediated food allergy may be what you would expect to see in an allergic reaction, such as:

  1. redness and itchiness of the skin – although not a raised, itchy red rash (hives)
  2. the skin becomes itchy, red, dry and cracked (atopic eczema)

Other symptoms can be much less obvious and are sometimes thought of as being caused by something other than an allergy. They include:

  1. vomiting with or without diarrhoea
  2. abdominal cramps
  3. constipation
  4. in babies: excessive and inconsolable crying, even though the baby is well fed and doesn’t need a nappy change (colic).

Symptoms of seafood allergy

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

But some people experience dangerous symptoms of anaphylaxis such as:

  1. difficulty breathing
  2. swelling of the tongue or tightness in the throat
  3. hoarse voice, wheezing or difficulty talking
  4. dizziness or collapsing due to a sudden drop in blood pressure

If you’re experiencing any of these dangerous symptoms, you need urgent medical assistance.

Call triple zero (000) or go straight to the emergency department of your nearest hospital.

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

Diagnosing seafood allergy

Allergies are caused by a reaction to specific proteins in foods. If you suspect you own an allergy, see your doctor, who can arrange appropriate skin or blood tests, and can assist you understand what these mean.

What causes sudden shellfish allergy

Your doctor can also prescribe an EpiPen for emergencies, if necessary.

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

Groups of fish:

  1. shark (sometimes called flake and commonly used in fish and chips)
  2. salmon, trout
  3. barramundi, bream, flathead, mackerel, perch, snapper, tuna, whiting
  4. sardines, anchovies and pilchards
  5. cod, haddock (often sold as ‘smoked’ fish) or hake
  6. sole, flounder

Allergy testing done under proper medical supervision is the only way to diagnose your specific seafood allergy.

Avoid testing methods advertised online or in print media.

What causes sudden shellfish allergy

Tests that are considered unreliable include hair analysis, Alcat or Vega tests, kinesiology, iridology, reflexology, pulse and cytotoxic food tests.


The symptoms of a severe allergic reaction (anaphylaxis) can be sudden and get worse extremely quickly.

Initial symptoms of anaphylaxis are often the same as those listed above and can lead to:

  1. swollen tongue
  2. tight chest
  3. feeling dizzy or faint
  4. breathing difficulties
  5. trouble swallowing or speaking
  6. collapse

Anaphylaxis is a medical emergency.

What causes sudden shellfish allergy

Without quick treatment, it can be life threatening. If you ponder you or someone you know is experiencing anaphylaxis, dial 999 and enquire for an ambulance as soon as possible.


What causes sudden shellfish allergy