Shellfish Allergy

Shellfish Allergy Guide: Symptoms, Causes, Diagnosis and Treatment

Overview

Shellfish allergy occurs when the immune system reacts to proteins found in shellfish. Reactions can range from mild symptoms such as skin rashes or stomach discomfort to severe allergic reactions including anaphylaxis.

Shellfish are usually divided into two main groups:

Crustaceans are the most common cause of shellfish allergy and are more likely to trigger severe reactions. Some people react to both groups, while others may only be allergic to one type.

Shellfish allergy is different from fish allergy, which involves species such as salmon, tuna, and cod.

Symptoms

In some cases, symptoms may occur after inhaling steam or vapours from cooking shellfish.

Diagnosis

If a shellfish allergy is suspected, a doctor or healthcare professional may refer you to an allergy specialist for further assessment. Diagnosis usually begins with a detailed medical history, including the symptoms experienced and foods eaten before the reaction.

Testing may include:

• Skin prick tests or blood tests to look for allergic antibodies
• Oral food challenge tests (carried out under medical supervision)
• Testing across different types of fish to determine which must be avoided

An allergy specialist will interpret test results alongside medical history, as tests alone do not always confirm a true food allergy.

Living with Shellfish Allergy

• Shopping: Shellfish must be clearly labelled on food packaging in many countries. Always read ingredient labels carefully, even on products you buy regularly, as recipes and manufacturing processes can change.
• Eating out: Tell restaurant staff about your shellfish allergy and ask how dishes are prepared. Shellfish may appear in soups, sauces, seafood dishes, and flavourings such as shrimp paste or oyster sauce.
• Cross-contact: Cross-contact can occur if foods are prepared using the same equipment or surfaces as shellfish. Seafood restaurants and kitchens that prepare multiple shellfish dishes may present higher risks.
• Airbourne exposure: In some people, inhaling vapours from cooking shellfish can trigger symptoms, particularly in enclosed kitchens or seafood markets.

Emergency Action

Mild allergic symptoms can often be treated with an antihistamine.

However, if there are signs of a severe allergic reaction — such as difficulty breathing, swelling of the throat or tongue, wheezing, sudden dizziness, or collapse — this is a medical emergency. Call your local emergency number immediately and use an adrenaline auto-injector if one has been prescribed.

Adrenaline auto-injectors commonly prescribed include:

• EpiPen® (adult and junior doses)
• Jext® (adult and junior doses)
• Auvi-Q® (available in some countries)

People at risk of severe allergic reactions are usually advised to carry two auto-injectors at all times, in case a second dose is needed.

After using an adrenaline auto-injector, medical attention is still required, as symptoms can return.

Friends, family members, teachers, and carers should know where the devices are kept and how to use them. Training devices and demonstration videos are available from the manufacturers’ websites.

Outgrowing Shellfish Allergy

Shellfish allergy is rarely outgrown and often continues into adulthood. However, some people may only react to specific types of shellfish.

Regular reviews with an allergy specialist can help determine whether the allergy is still present and which foods should be avoided.

Future Treatments

Research into new treatments for food allergies is ongoing. Some emerging approaches include:

Oral immunotherapy (OIT) – gradually introducing very small amounts of the allergen under medical supervision to help build tolerance.

Epicutaneous immunotherapy – skin patch treatments designed to slowly desensitise the immune system.

New medicines and biological therapies – researchers are studying treatments that may help reduce the severity of allergic reactions.

Many of these treatments are still being studied and may not be suitable for everyone.

For now, the safest approach remains avoiding trigger foods, checking ingredient labels carefully, and carrying emergency medication if prescribed.

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When to Seek Medical Advice

Speak to a doctor or healthcare professional if you think you or your child may have a food allergy. Symptoms such as hives, swelling, stomach pain, vomiting, or breathing problems after eating certain foods should always be assessed by a medical professional.

Urgent medical attention is needed if symptoms of a severe allergic reaction (anaphylaxis) occur, including difficulty breathing, swelling of the throat or tongue, wheezing, dizziness, or collapse.

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Resources

• NHS – Food Allergy Guidance
• Allergy UK
• British Society for Allergy & Clinical Immunology (BSACI)

These organisations provide trusted information, advice, and support for people living with allergies.

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Medical Disclaimer

This guide is provided for general information only and is not a substitute for professional medical advice, diagnosis, or treatment.

Always seek advice from your doctor, allergy specialist, or another qualified healthcare professional if you have concerns about allergies, symptoms, or treatment.

If you believe you or someone else may be experiencing a severe allergic reaction (anaphylaxis), seek emergency medical assistance immediately.

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