Shellfish Allergy – Symptoms and Causes
Overview
Shellfish allergy occurs when the immune system reacts abnormally to proteins found in certain marine animals. This category includes both crustaceans (like shrimp, crabs, and lobster) and mollusks (such as squid, oysters, scallops, and snails).
Many people with this common food allergy may react to all types of shellfish, while others only experience reactions to specific kinds.
Symptoms vary widely in severity, including:
- Mild reactions (hives, stuffy nose)
- Moderate symptoms
- Severe, potentially life-threatening responses
If you suspect you have a shellfish allergy, it’s important to consult with a healthcare provider. Medical tests can confirm the allergy, allowing you to take appropriate precautions to prevent future allergic reactions.
Signs and Symptoms
When someone has a shellfish allergy, they typically notice symptoms within minutes to an hour of eating or touching shellfish. These symptoms may include:
- Skin reactions – hives and itchy skin
- Swelling – particularly of the lips, face, tongue and throat
- Breathing problems – wheezing, coughing or trouble breathing
- Nasal issues – congestion
- Digestive problems – stomach pain, diarrhea, nausea or vomiting
- Balance issues – dizziness, lightheadedness or fainting
Severe Allergic Reaction
A shellfish allergy can trigger a severe, life-threatening allergic reaction. This serious reaction happens quickly after exposure and gets worse rapidly.
This type of severe reaction needs emergency treatment right away with an epinephrine injection followed by a trip to the emergency room. Without fast treatment, it can be deadly.
During a severe reaction, the body releases many chemicals that can cause shock. Signs include:
- Throat or tongue swelling makes breathing difficult
- Trouble breathing with coughing or wheezing
- Drop in blood pressure with fast or weak pulse
- Severe skin reactions including rash, hives, or swelling
- Stomach issues like nausea, vomiting, or diarrhea
- Feeling dizzy or faint
When Medical Help Is Needed
Get emergency help right away if you notice signs of a severe allergic reaction.
Make an appointment with a doctor or allergy specialist if you have any food allergy symptoms soon after eating. Early diagnosis can help manage the condition and prevent serious reactions.
What Causes Shellfish Allergies
Shellfish allergies happen when the body’s immune system makes a mistake. It sees proteins in shellfish as harmful when they are actually safe. When this happens, the immune system creates special antibodies called immunoglobulin E (IgE) to fight these proteins.
The next time you eat shellfish, these antibodies tell your body to release chemicals like histamine. These chemicals cause the symptoms of an allergic reaction, such as a rash, swelling, or breathing problem.
Different Types of Shellfish
Shellfish come in several varieties, and each contains different proteins that may trigger allergies:
Crustaceans:
- Crabs
- Lobster
- Crayfish
- Shrimp
- Prawn
Mollusks:
- Squid
- Octopus
- Mussels
- Snails
- Clams
- Oysters
- Abalone
- Scallops
Most shellfish allergies involve crustaceans, but reactions vary from person to person. Some people might be allergic to just one type of shellfish while others need to avoid all kinds.
It’s important to note that fish allergies (to salmon, tuna, etc.) are different from shellfish allergies. If you have a shellfish allergy, you might still be able to eat fish safely.
Some people, however, are allergic to both. A healthcare provider can help determine which seafood is safe for you to eat.
Risk Factors
Shellfish allergies tend to run in families. If your relatives have allergies, you may be more likely to develop a shellfish allergy too.
Adults get shellfish allergies more often than children. This allergy is the most common food allergy among adults. Women are more affected than men in adult groups. For children who develop this allergy, boys are affected more frequently than girls.
Possible Complications
Severe shellfish allergies can cause anaphylaxis, a potentially life-threatening reaction requiring immediate medical attention.
Several factors increase anaphylaxis risk:
- Asthma
- High sensitivity to tiny amounts of shellfish
- Previous anaphylactic reactions to food
- Strong family history of allergies
People who experience severe shellfish allergic reactions should always carry injectable epinephrine (like Auvi-Q or EpiPen). This emergency medication delivers adrenaline to counteract the dangerous symptoms of anaphylaxis.
How to Stay Safe
Steering Clear of Shellfish
For people with shellfish allergies, complete avoidance is essential. Even tiny amounts can trigger severe reactions in sensitive individuals.
When eating out:
- Ask if cooking tools are shared between shellfish and other foods
- Consider avoiding seafood restaurants entirely due to cross-contamination risks
- Inform servers clearly about your allergy
Check product labels carefully:
- Look for shellfish in ingredient lists
- Be aware that shellfish might be in fish stock or seafood flavoring
- Remember that while crustacean shellfish must be labeled by law, mollusks don’t require the same labeling
You may need to avoid places where shellfish are prepared. Some people react to touching shellfish or breathing steam from cooking shellfish.
Safety Preparations
Taking these precautions can help protect you:
- Discuss emergency epinephrine with your healthcare provider.
- Learn how to use your emergency medication properly.
- Wear a medical alert bracelet or necklace that identifies your allergy.
These simple steps can save precious time during an emergency reaction.
About Iodine and Contrast Dyes
Despite common misconceptions, a shellfish allergy doesn’t mean you’ll react to iodine or radiocontrast materials used in imaging tests.
Shellfish contain small amounts of iodine, but the allergic reaction to shellfish is unrelated to reactions some people have to radiocontrast materials or iodine. This means you can safely undergo necessary medical imaging that requires contrast dye.
