Shellfish Allergies
Evidence-based information about symptoms, diagnosis, and management of shellfish allergies
What are Shellfish Allergies?
Shellfish allergies are one of the most common food allergies, especially among adults. These allergies can cause severe, potentially life-threatening allergic reactions. Shellfish allergies typically develop during adulthood, although they can appear at any age.
Unlike many food allergies that children outgrow, shellfish allergies are usually lifelong once developed. The allergy is caused by an immune system reaction to proteins found in certain marine animals.
Important Note
If you suspect you have a shellfish allergy, consult with an allergist for proper diagnosis before making dietary changes.
Types of Shellfish That Cause Allergies
Shellfish are divided into two groups: crustaceans and mollusks. Most shellfish allergies are triggered by crustaceans, but some people may be allergic to both groups.
Crustaceans
- Shrimp
- Crab
- Lobster
- Crayfish
- Prawns
Mollusks
- Clams
- Mussels
- Oysters
- Scallops
- Squid (calamari)
- Octopus
- Snails
If you're allergic to one type of shellfish, your allergist may recommend avoiding all shellfish due to the risk of cross-contamination and potential cross-reactivity between different types.
Symptoms of Shellfish Allergies
Allergic reactions to shellfish can range from mild to severe and can affect various body systems. Symptoms typically appear within minutes to hours after consuming shellfish or foods containing shellfish proteins.
Common Symptoms
- Skin Reactions
- Hives, itching, redness, swelling, eczema flare-ups
- Digestive Issues
- Abdominal pain, nausea, vomiting, diarrhea, difficulty swallowing
- Respiratory Symptoms
- Runny or stuffy nose, sneezing, coughing, wheezing, shortness of breath
- Severe Reactions
- Anaphylaxis: rapid pulse, drop in blood pressure, constriction of airways, dizziness, loss of consciousness
Emergency Warning
Anaphylaxis is a medical emergency that requires immediate treatment with epinephrine (adrenaline) and a trip to the emergency room. If you or someone you're with is experiencing signs of anaphylaxis, use an epinephrine auto-injector if available and call emergency services immediately.
Diagnosis and Testing
If you suspect you have a shellfish allergy, it's important to see an allergist for proper diagnosis. Self-diagnosis can lead to unnecessary dietary restrictions or failure to identify a potentially serious allergy.
Diagnostic Methods
Medical History
Your allergist will ask detailed questions about your symptoms, when they occur, and your dietary habits.
Skin Prick Test
A small amount of shellfish protein is placed on your skin, and the skin is pricked to allow the substance to enter. If you're allergic, you'll develop a raised bump (wheal) at the test site.
Blood Test
Measures the amount of shellfish-specific IgE antibodies in your blood. Higher levels can indicate an allergic sensitivity.
Oral Food Challenge
Under medical supervision, you consume small amounts of shellfish to see if a reaction occurs. This is typically done when other tests are inconclusive.
Your allergist will interpret the results of these tests in the context of your medical history to make an accurate diagnosis.
Managing Shellfish Allergies
Currently, there is no cure for shellfish allergies. Management involves strict avoidance of shellfish and being prepared for accidental exposure.
Avoidance Strategies
- Read food labels carefully. Look for statements like "Contains shellfish" or "May contain traces of shellfish."
- Be cautious when dining out, especially at seafood restaurants where cross-contamination is likely.
- Ask about ingredients when dining out. Inform servers and kitchen staff about your allergy.
- Be aware of hidden sources of shellfish, such as fish sauce, seafood flavoring, and surimi.
- Be cautious with Asian cuisine, which often contains shellfish or shellfish-derived ingredients.
Emergency Preparedness
- Carry an epinephrine auto-injector (such as EpiPen® or Auvi-Q®) at all times if prescribed.
- Wear a medical alert bracelet or necklace indicating your allergy.
- Create an emergency action plan with your healthcare provider.
- Educate family members, friends, and colleagues about your allergy and how to help in an emergency.
Emerging Treatments
Research into treatments for food allergies, including shellfish allergies, is ongoing. Some promising approaches include:
- Oral Immunotherapy (OIT): Gradually introducing increasing amounts of the allergen under medical supervision to build tolerance.
- Epicutaneous Immunotherapy (EPIT): Delivering small amounts of the allergen through a patch on the skin.
- Biologics: Medications that target specific pathways in the allergic response.
These treatments are still being studied and are not yet widely available. Consult with your allergist about whether any of these approaches might be appropriate for you.