What Is a Shellfish Allergy?
A shellfish allergy occurs when the body’s immune system mistakenly identifies proteins in shellfish as harmful, triggering an allergic response. Shellfish can be divided into two groups:
- Crustaceans: Such as prawns, crab, lobster, yabbies, and Moreton Bay bugs.
- Molluscs: Such as oysters, mussels, scallops, squid, and octopus.
Crustaceans are more commonly linked to severe allergic reactions. In Australia, shellfish allergy is a significant concern, especially for those in coastal communities or working in food-related industries.
Shellfish vs. Other Seafood Allergies
It’s important to note that being allergic to shellfish does not necessarily mean you are allergic to fish (such as salmon or tuna). Fish and shellfish are biologically different. However, individuals allergic to one type of shellfish (e.g. prawns) may react to other types.
Common Shellfish Types That Trigger Allergies
Common triggers include:
- Crustaceans: Prawns, crabs, lobsters, yabbies.
- Molluscs: Oysters, mussels, scallops, squid.
Crustaceans are more likely to cause allergic reactions.
Causes and Risk Factors of Shellfish Allergies
A shellfish allergy is caused by an immune response where the body misidentifies shellfish proteins as dangerous. This triggers the release of chemicals like histamine, leading to symptoms.
Why Shellfish Allergies Can Develop Later in Life
Unlike many other food allergies that begin in childhood, shellfish allergies often develop during adulthood. Researchers suggest it could be linked to increased exposure over time or changes in immune system function.
Risk Factors Specific to Australians
Australians with a seafood-heavy diet or those working in coastal regions may face higher risks. Occupational exposure, particularly in food service, hospitality, and food handling jobs, increases the chance of developing an allergy.
Symptoms of a Shellfish Allergy
Symptoms usually appear within minutes to an hour after eating shellfish.
Mild to Moderate Symptoms
- Hives or skin rash
- Itchy mouth, lips, or throat
- Nasal congestion
- Stomach pain, vomiting, or diarrhoea
Severe Reactions (Anaphylaxis)
Anaphylaxis is a medical emergency. Signs include:
- Swelling of the lips, tongue, or throat
- Difficulty breathing
- Dizziness or fainting due to low blood pressure
- Rapid pulse
Immediate treatment with an adrenaline auto-injector (e.g. EpiPen) and a call to 000 is essential.
Diagnosing a Shellfish Allergy
See your GP for a referral to an allergist or immunologist. Diagnostic options include:
- Skin prick tests
- Blood tests (specific IgE)
- Medically supervised food challenges
Medicare may cover part of the cost for testing with a valid referral.
What to Expect at a Medical Appointment
Your doctor will take a detailed history and arrange for tests. Allergy tests are safe and crucial for proper management.
Self-Assessment and Why It’s Not Enough
Avoid self-diagnosing or eliminating shellfish without medical advice, as this can lead to nutritional imbalance or delayed diagnosis.
Managing Shellfish Allergies at Work and in Daily Life
Reading Food Labels in Australia
By law, packaged food must declare the presence of shellfish in the ingredient list or under “Contains” statements. Be alert for “May contain” warnings due to cross-contamination risk.
Avoiding Cross-Contamination in Shared Kitchens
- Use separate utensils and cookware.
- Clean surfaces thoroughly.
- Store shellfish away from allergen-free food.
Safety in Hospitality or Food Handling Jobs
If you work in food handling, wear PPE as needed, and notify your employer of your allergy. Employers have responsibilities under Australian WHS laws to provide a safe workplace.
What to Do During an Allergic Reaction
Creating an Allergy Action Plan
Work with your doctor to develop a written plan. The Australasian Society of Clinical Immunology and Allergy (ASCIA) provides templates.
How to Use an EpiPen
- Remove the blue safety cap.
- Place the orange tip against your outer thigh.
- Push down until you hear a click.
- Hold for 3 seconds, then remove.
Always call 000 after using an EpiPen.
Travelling and Eating Out with a Shellfish Allergy
Tips for Dining Out
- Inform staff of your allergy.
- Ask about ingredients and cooking practices.
- Consider carrying allergy translation cards.
Travel Advice for Australians
- Pack safe snacks.
- Carry medications in hand luggage.
- Check that your travel insurance covers allergy-related emergencies.
Living Well with a Shellfish Allergy
Support Groups and Resources
- Allergy & Anaphylaxis Australia
- ASCIA
- Online communities for peer advice
Emotional and Mental Health Support
Living with a food allergy can be stressful. Seek counselling if anxiety interferes with daily life.
FAQ
Can you suddenly develop a shellfish allergy as an adult?
Yes, many people develop shellfish allergies in adulthood, often without prior warning.
What are the most common shellfish people are allergic to?
Prawns and other crustaceans are the most common triggers.
How do I know if I have a shellfish allergy or food poisoning?
Shellfish allergy symptoms usually occur within minutes to an hour and can include hives, swelling, and breathing difficulty. Food poisoning symptoms often develop several hours later and usually cause vomiting or diarrhoea without hives or swelling.
Is there a cure for shellfish allergy?
There is no cure. The best management is strict avoidance and emergency preparedness.
Can I be allergic to only one type of shellfish?
Yes, although cross-reactivity is common.
Are shellfish allergies inherited?
There may be a genetic predisposition, but having a family history does not guarantee you will develop an allergy.
What should I do if I accidentally eat shellfish?
Follow your action plan, use an EpiPen if prescribed, and call 000.
Is shellfish allergy the same as iodine allergy?
No, they are unrelated. Shellfish allergy is to proteins, not iodine.
Do I need to carry an EpiPen if I have a mild allergy?
Discuss this with your doctor. Even mild reactions can become severe unexpectedly.
How do I keep safe from shellfish at work or in restaurants?
Disclose your allergy, check labels, avoid high-risk foods, and follow cross-contamination prevention practices.
Key Points
- Shellfish allergy is common in adults and can be severe.
- Reactions range from mild itching to life-threatening anaphylaxis.
- Proper diagnosis and an action plan are crucial.
- Cross-contamination is a major risk, especially in food handling jobs.
- With the right knowledge and support, Australians with shellfish allergy can live safely and confidently.
