Identifying Shellfish Allergy Symptoms
Reactions to Crab, Lobster, Crawfish, and Shrimp
Medically reviewed by Jurairat J. Molina, MD
A food allergy occurs when the body’s immune system overreacts to a certain food. The reaction can range from mild to severe to life-threatening. A shellfish allergy is the one of the most common types of food allergy in the United States. It usually affects adults but may develop in childhood. A shellfish allergy is different than a fish or seafood allergy.
People with a shellfish allergy are allergic to crustaceans (shrimp, lobster, crab) and mollusks (scallops, oysters, clams, mussels). A shellfish allergy reaction can affect the skin, respiratory, gastrointestinal (GI), and cardiovascular systems. Mild symptoms of a shellfish allergy include nausea, vomiting, and diarrhea. Severe symptoms include hives and trouble breathing.
This article will provide an overview of shellfish allergy including the symptoms and how to manage them.
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Mild Shellfish Allergy Symptoms
Mild symptoms of a shellfish allergy are uncomfortable but not life-threatening. They often affect the gastrointestinal tract and may include:
Indigestion
Stomach cramping
Vomiting
Other mild symptoms may include a red, itchy rash or a runny nose.
Explainer
Shellfish allergy symptoms are usually classified as mild or severe. Mild symptoms are uncomfortable but not dangerous. Severe symptoms can become life-threatening if left untreated. If you are unsure if your symptoms are severe, call 911.
Emergency Shellfish Allergy Symptoms
A shellfish allergy can cause anaphylaxis, an emergency reaction that causes the throat to swell and close up. Severe shellfish allergy symptoms can become life-threatening in a very short amount of time. It is important to treat them immediately.
Emergency shellfish allergy symptoms may include:
Wheezing
Coughing
Shortness of breath
Trouble breathing
Hives
Weak pulse
Pale or blue-tinged skin color
Facial swelling
Confusion
Inject Epinephrine If You Have It
If you or someone you are caring for begins to experience anaphylaxis, take epinephrine immediately. Epinephrine is a first-line medication for anaphylaxis. It comes in the form of a small device called an auto-injector. This device contains a needle that can inject medication quickly in an emergency.
Use your epinephrine auto-injector, such as an EpiPen, if you develop any of the following symptoms after eating shellfish:
Shortness of breath
Throat tightness
Repetitive coughing
Trouble swallowing
Facial swelling
Hives
Weak pulse
Your healthcare provider will likely recommend keeping two doses of epinephrine with you because an allergic reaction can recur after the first dose.
Epinephrine may cause side effects, including:
Anxiety
Restlessness
Dizziness
Shakiness
If you are unsure if you are experiencing anaphylaxis, it is better to use epinephrine than to wait.
Call 911
After injecting epinephrine, call 911. When you call, tell the dispatcher that you or the person you are with is experiencing an allergic reaction. Tell the dispatcher how many epinephrine doses you gave and request the paramedics bring an additional dose.
What Seafood Is Considered Shellfish?
A shellfish allergy is different from a fish or seafood allergy. A shellfish allergy includes two types of fish, which are:
Crustacean group: Shrimp, lobster, crab
Mollusks group: Scallops, oysters, clams, mussels
The crustacean group is responsible for the greatest number of allergic reactions. Some people with a shellfish allergy may be able to tolerate mollusks safely.
Explainer
Some people who cannot tolerate shellfish may have an intolerance or sensitivity, rather than a true allergy. A food allergy affects the entire body. Food intolerance or sensitivity affects only the GI tract. While food intolerance and sensitivity can cause very uncomfortable symptoms, they are never life-threatening.
Crossover Between Fish and Shellfish Allergies
It is possible to be allergic to both shellfish and fish. Some people with a shellfish allergy also react to fish like tuna or cod.
Even if you do not have a fish allergy, it is important to use caution when ordering seafood at a restaurant. Fish and shellfish are often stored together, and they may touch each other. This is referred to as cross-contamination.
What to Do for Mild Shellfish Allergy Reactions
A mild shellfish allergy usually causes stomach upset like diarrhea or vomiting. It is very uncomfortable but not life-threatening.
Ask your healthcare provider how to safely manage a mild shellfish allergy. The best treatment is to avoid all shellfish. If this is not possible, your provider may recommend an antihistamine allergy medication.
Testing to Confirm a Shellfish Allergy
The only way to know if you have a shellfish allergy is to undergo allergy testing. For allergy testing, your healthcare provider will likely refer you to an allergist, a medical doctor who specializes in diagnosing and treating allergies.
First, the allergist will ask you several questions about your allergic reactions, including:
Which foods did you eat?
How big a portion did you eat?
What symptoms did you experience?
When did the symptoms develop?
How long did the symptoms last?
If your allergist suspects that you have an allergy, they will recommend allergy testing. Testing options include:
Skin-prick test: The allergist places a drop of liquid that contains proteins from shellfish on the skin of your arm or back. The skin is then pricked so that the liquid goes under the skin's surface. The allergist observes the area for reaction for about 15 to 30 minutes. A reaction looks like a red, itchy bump.
IgE blood test: The allergist measures the amount of immunoglobulin (IgE) antibodies in the blood. The immune system makes antibodies against shellfish if you have an allergy. This blood test is able to check for the specific type of IgE and its level.
Oral-challenge test: Under the supervision of your allergist, you will be asked to slowly eat a small amount of shellfish to see if you have a reaction. The allergist will have emergency medication ready if needed.
Food-elimination diet: A food-elimination diet involves removing shellfish from your diet for two weeks and then slowly adding it back in to see if you have a reaction. If you have had a serious reaction in the past, this test is not considered safe.
The food challenge test is the only allergy test that can confirm a true food allergy. If your allergy testing reveals that you are allergic to shellfish, your allergist will prescribe an epinephrine auto-injector to keep with you at all times.
Learn More: The Difference Between Blood Tests and Skin Tests for Allergies
How to Stay Ahead of Shellfish Reactions
The best way to prevent a shellfish allergy reaction is to avoid all shellfish. However, this can be more challenging than it sounds.
Many grocery stores and restaurants store their fish and shellfish together. Your allergist may recommend that you avoid any seafood or seafood restaurants. A person with a severe shellfish allergy may react to food that was cooked near shellfish because of the vapors in the air. It is also possible to react to certain fried foods because the frying oil may have been used for clams.
When grocery shopping, carefully check ingredient labels for fish or shellfish. Fortunately, crustacean seafood must be listed in clear language on all food products according to the Food Allergen Labeling and Consumer Protection Act of 2004.
Explainer
People with a shellfish allergy react to a protein in shellfish called tropomyosin. In the past, people with a shellfish allergy were told to avoid iodine dye found in radiocontrast media for medical procedures.
Research has found that iodine does not contain the protein in shellfish that causes the allergy, so it is considered safe. People with a shellfish allergy can also consume glucosamine, a supplement made from shells, because it does not contain the protein.
Summary
People with food allergies experience an immune system overreaction when they are exposed to that food. A shellfish allergy is the most common type of food allergy in the United States. It usually develops in adulthood. Shellfish includes crustaceans (shrimp, lobster, crab) and mollusks (scallops, oysters, clams, mussels).
Mild symptoms of a shellfish allergy include indigestion, nausea, vomiting, and diarrhea. A severe reaction may cause shortness of breath, trouble swallowing, hives, and facial swelling. A shellfish allergic reaction can affect the skin, respiratory tract, gastrointestinal tract, and cardiovascular system. To prevent an allergic reaction, avoid all types of shellfish. If you are exposed and develop a severe reaction, use your epinephrine auto-injector and call 911.
Read the original article on Verywell Health.
