What is Shellfish Allergy?
Shellfish reactions are often caused by the immune system or non-immune related responses. Figuring out what’s causing the reaction in the patient is key to determining the right course of treatment and understanding how to manage it. The most common cause of shellfish allergies is a protein named Tropomyosin.
The term ‘shellfish’ includes a large variety of seafood, such as crustaceans (like crab or shrimp) and mollusks (like clams or scallops). This makes dealing with shellfish allergies more challenging. Not everyone who is allergic to shellfish reacts to both types. In fact, studies suggest that only around 14% of people have cross-allergies to both crustacean and mollusk.
What Causes Shellfish Allergy?
If you have a reaction or symptoms after eating shellfish, it can be due to different reasons. Sometimes, it’s not actually a true allergy but could be due to harmful things like parasites, bacteria, or viruses. Certain bacteria like Vibrio, Listeria, and Salmonella are commonly associated with shellfish.
There are also instances when toxins, which are harmful substances produced by certain plants, animals, or bacteria, can cause reactions. For example, toxins like ciguatera or saxitoxin can lead to symptoms if you eat affected shellfish.
However, true allergic reactions are also possible. They can occur from substances in the shellfish, like tropomyosins, which are proteins found in the muscle tissue. Allergies can also come from components eaten with the shellfish like spices or chemical additives.
Risk Factors and Frequency for Shellfish Allergy
Fish and shellfish are thought to be responsible for a significant number of allergic reactions. It’s hard to pin down the exact number of shellfish allergies because there can be many causes and often these allergies are not reported fully. Even when an allergy is confirmed, it can be hard to figure out if a chemical or other additive triggered it. In general, food allergens cause about 30,000 serious allergic reactions known as anaphylaxis. Roughly one-third of all anaphylaxis cases are caused by food.
Signs and Symptoms of Shellfish Allergy
If you’ve recently eaten or handled shellfish or snails, and you begin experiencing allergic reactions within a few minutes or hours, you might have a shellfish allergy. These reactions differ from person to person—while some people may experience relatively mild symptoms like itching and hives, others could have severe symptoms like difficulty breathing or low blood pressure (anaphylaxis). Various other symptoms can be associated with shellfish allergies, including:
- Skin inflammation (eczema)
- Cough or sneeze
- Runny nose
- Tingling around the mouth
- Nausea, diarrhea, or vomiting
- Dizziness or fainting
Testing for Shellfish Allergy
If you’re having symptoms after eating shellfish and your doctor suspects an allergy, they’re likely to diagnose it based on your symptoms and physical signs rather than relying on quick tests – none currently exist that can accurately diagnose shellfish allergies. Monitoring crucial signs like your breathing and blood pressure really helps doctors determine if you’re having a severe allergic reaction, called anaphylaxis, or a less serious reaction.
They’ll listen closely with a stethoscope to your lungs for wheezing or other abnormal sounds and also look at the back of your throat. Additionally, since many people with shellfish allergies have stomach issues, they’ll also do a thorough check of your abdominal area. Another part of the diagnosis involves looking closely at your skin for any rashes or swelling.
When it comes to testing for specific toxins sometimes found in shellfish, different techniques can be used. For example, for domoic acid, doctors might use methods like mass spectrometry, liquid chromatography, and enzyme-linked immunosorbent assay – or ELISA. If they need to test for Saxitoxin, they’ll likely use a mouse bioassay, ELISA, and high-performance liquid chromatography. And for brevetoxin, they might use an antibody radioimmunoassay (similar to ELISA), a mouse bioassay, and ELISA.
Treatment Options for Shellfish Allergy
Currently, there are no specific treatments for shellfish allergies. The best way to manage this type of allergy is to avoid consuming shellfish that may trigger an allergic reaction. In certain cases, steps can also be taken to prevent potentially contaminated fish from entering our food supply, which can help prevent allergy-related incidents.
If an allergic reaction does occur, treatments often involve providing necessary care to ease symptoms and ensure the patient’s safety. For instance, if a person has been vomiting due to a severe allergic reaction, they may be given intravenous fluids to keep them hydrated. Other treatments include antihistamines, which are drugs that can help to reduce allergy symptoms, and steroids, which can help to decrease inflammation in the body.
In more severe cases, where a person experiences anaphylaxis (a severe, potentially life-threatening allergic reaction), emergency treatment might be needed. This usually includes the immediate administration of a drug called epinephrine, which can rapidly reverse the symptoms of an anaphylactic reaction. After this, antihistamines, steroids, and IV fluids may be administered. In extremely rare cases, if the usual treatments don’t work, a procedure called intubation could be necessary to protect the patient’s airways.
The length of time that symptoms last and how patients respond to treatment can vary greatly. Some people might respond quickly to treatment and begin improving while still in the emergency department. These patients can often return home safely with a prescription for oral antihistamines and steroids. They’re also given instructions to return to the hospital if their symptoms get worse. However, severe cases, such as anaphylaxis, would require hospital admission for further monitoring and close observation.
After treatment, patients are advised to avoid the food that triggered their allergic reaction. For example, a person who has had an allergic reaction to crabs should avoid other types of crustaceans. Even with careful avoidance, doctors might recommend that patients have an epinephrine auto-injector at hand. This is a device that can administer a dose of medicine quickly in case of anaphylaxis, and it’s particularly helpful due to the potential for severe allergenic reactions and cross-reactions with other similar allergens.
What else can Shellfish Allergy be?
If a person is experiencing symptoms that suggest a shellfish allergy, doctors need to rule out other conditions that could cause similar symptoms. These include:
- Acute urticaria (hives)
- Bacterial gastroenteritis (an infection in the stomach)
- Bulimia nervosa (an eating disorder)
- Celiac disease (an autoimmune condition affecting the gut)
- Chronic gastritis (long-term inflammation of the stomach lining)
- Constipation
- Diverticulitis (inflammation of pouches in the digestive tract)
- Dumping syndrome (a condition where food moves too quickly from the stomach to the small bowel)
- Esophageal spasm (abnormal contractions in the esophagus)
- Esophageal stricture (narrowing of the esophagus)
By considering these possibilities and conducting appropriate tests, an accurate diagnosis can be made.
What to expect with Shellfish Allergy
In 2017, the National Poison Data System (NPDS), which reports on poison cases in America, noticed patients suffering from a specific type of poisoning called paralytic shellfish poisoning. This issue comes from eating shellfish infected with toxins produced by harmful algae blooms, also known as HAB toxins.
Out of 109 cases, there were 3 severe results, 20 moderately severe outcomes, and 17 mild outcomes. Thankfully, there were no deaths reported. It’s worth noting that people with chronic illnesses like liver disease may become more seriously ill if they get this type of poisoning.
Paralytic shellfish poisoning is the worst type of shellfish poisoning. The mortality rates from this condition range between 1% and 12%. In especially severe cases, it can cause muscle paralysis and respiratory failure, leading to death within 2 to 25 hours. On a more positive note, the chances of death decrease if medical professionals can quickly provide high-level life support.
Possible Complications When Diagnosed with Shellfish Allergy
Shellfish poisoning can manifest in five unique ways due to the toxins present. Here’s what you need to know:
- Paralytic shellfish poisoning: After eating spoiled shellfish, symptoms typically start within 2 hours but can take anywhere from 15 minutes to 10 hours to show up. Initial symptoms include a tingling sensation in the area around the mouth, lips, tongue, and gums. This quickly spreads to the arms and legs. Other symptoms may involve a headache, paralysis, trouble walking, muscle weakness, and issues related to cranial nerves.
- Neurologic shellfish poisoning: This type of poisoning is less severe than paralytic shellfish poisoning. Symptoms usually include upset stomach, a burning feeling in the entirety of the large intestine, and tingling sensations in the face, limbs, and trunk. Other potential symptoms include muscle pain, spinning sensation, balance problems, and not being able to tell hot from cold.
- Diarrheal shellfish poisoning: Symptoms typically develop between 30 minutes to a few hours after consuming contaminated shellfish. These primarily include severe diarrhea, stomach cramps, nausea, and vomiting. There may also be a feeling of chills.
- Amnesic shellfish poisoning: Symptoms can occur within 24 hours of consuming toxic shellfish, including diarrhea, vomiting, and abdominal pain. This can be followed by headaches, memory loss, and cognitive decline.
- Azaspiracid shellfish poisoning: Consumption of contaminated shellfish may lead to nausea, vomiting, diarrhea, and stomach cramps.
Preventing Shellfish Allergy
Doctors should inform their patients about certain food items that can cause harmful reactions in the body. It’s also important to educate patients about the early signs of a shellfish allergy, so they can get medical help promptly if these signs appear. In collaboration with other healthcare professionals, doctors should also tell patients to seek immediate medical assistance if they are unable to drink liquids, if they have a fever, if they notice blood in their stool, or if they develop any other concerning symptoms.