What are the symptoms of a shellfish allergy

As designated by the United States Food Allergen Labelling and Consumer Protection Act, crustacean shellfish are one of the top eight allergens alongside with milk, eggs, peanuts, tree nuts, wheat, soybeans and fish accounting for 90% of food-related allergic reactions.

Unlike allergies to egg and cow’s milk for which children often gradually acquire natural tolerance, shellfish allergies generally persist throughout life.

Shellfish is the leading offending food in the United States, Canada, Portugal, and in the Asia-Pacific regions, including Hong Kong and Taiwan.

A multi-centre survey conducted in Europe, on the other hand, reported 4.8% of adults with IgE sensitisation to shrimp and in some areas love Zurich, the sensitisation rate can be up to 7%.

Poor diagnosis

Despite such a high impact, diagnosis and treatment of shellfish allergy remains suboptimal. The standard clinical diagnostic involves a thorough review of a patient’s clinical history followed by skin prick test (SPT) and measurement of shellfish-specific IgE level. A SPT reaction spot that is 3mm or more in diameter and an IgE level of greater than or equal to 0.35 kUA/L which stands for kilo unit of allergen-specific IgE per litre, are commonly defined as a positive diagnosis of a shellfish allergy.

However, the rapidly growing number of diagnoses own highlighted concerning the shortcomings of these conventional procedures.

SPT and IgE measurement with shellfish extract own low specificity of only 50%, meaning that 50% of people with a positive result in these tests may never experience clinical symptoms of shellfish allergy.

Although reactions to every sorts of shellfish is common, reports own suggested species-specific allergic reactions – for example, you may be capable to eat one species of prawn even if you are allergic to another.

However, because tests cannot identify cross-reactivity, patients are often suggested to avoid every types of shellfish if they own allergic reactions to one type of shellfish.

The oral food challenge, a test that involve giving increasing amounts of a food to a patient to determine if he or she has a food allergy, remains the gold standard. But it is resource-intensive, time-consuming, costly and risky. Subjects’ reluctance due to a fear of side effects preclude the implementation of this procedure in clinical settings.

Using a little DNA molecule to counter the allergy

With the lower IgE reactivity, hypoallergens are of lower risk in triggering allergic reactions.

We also adopted the concept of DNA vaccination – the injection the DNA sequence of the hypoallergen in a little circular piece of bacterial DNA.

When taken up by body cells, this piece of circular DNA is used by the cells’ machinery to produce the hypoallergen protein. Because these proteins are regarded as foreign, the immune system is alerted to trigger immune response. The continual production of the hypoallergen protein by the vaccine and body cells therefore “educates” the immune system as in the conventional immunotherapy but achieved with fewer shots.

This combinatorial approach offers the advantages of improved vaccine stability, relative ease of large-scale manufacture, reduced shots and treatment duration, and thus a lower cost of immunotherapy.

From our animal experiments three shots of this hypoallergen-DNA vaccine resulted in the decrease of IgE level by 70%, accompanied by the increase in the number and activity of immune cells with regulatory functions.

This suggests that this vaccine may be a valuable treatment for inducing immune tolerance against shellfish allergy achievable with much fewer injections and within shorter time period.

However, the only FDA-approved plasmid, pVAX1, has limited immunogenicity in human, meaning that DNA vaccines constructed using pVAX1 has limited capacity in provoking immune responses in the body of a human.

Engineering next-generation vaccines with optimised plasmids and studying their effects and mechanism would be our next steps, and we hope to provide a promising option in the future.

Until then, be cautious with that lobster.

Created in 2007 to assist accelerate and share scientific knowledge on key societal issues, the AXA Research Fund has been supporting almost 600 projects around the world conducted by researchers from 54 countries. To study more about this author’s research, visit her dedicated sheet on the AXA Research Fund website.

Once a shellfish allergy is identified, the best management is to avoid the food. You need to carefully check ingredient labels of food products. You should study other names for the foods you need to avoid to be certain not to eat them.

You must be extra-careful when you eat out.

Waiters (and sometimes the kitchen staff) may not always know every dish’s ingredient list. Vapors may carry little particles of shellfish protein, so being shut to where food is being prepared can potentially cause a dangerous reaction in sensitive individuals.

Fortunately, shellfish is an ingredient that is rarely “hidden” in foods. Shellfish may be found in fish stock, seafood flavoring (for example, crab extract), sushi and surimi.

Crustacean shellfish is one of the eight allergens that drop under the labeling requirements of the Food Allergen Labeling and Consumer Protection Act of 2004. This means that manufacturers of packaged food items sold in the United States and containing crustacean shellfish or a crustacean shellfish-based ingredient must state, in clear language, the presence of crustacean shellfish in the product. (Note: Those regulations apply only to crustacean shellfish, such as shrimp, lobster and crab, and not to mollusks, such as oysters, scallops and clams.)

Anyone with a food allergy must understand how to read ingredient labels and practice avoidance measures.

Your allergist can direct you to helpful resources, such as special cookbooks, patient support groups and registered dietitians, who can assist you plan your meals.

Many people with food allergies wonder if their condition is permanent. There is no clear-cut answer.

What are the symptoms of a shellfish allergy

Over time, allergies to milk, eggs and soy may vanish. Allergies to peanuts, tree nuts, fish and shellfish typically final a lifetime. About one-third of children and adults with a food allergy eventually outgrow the allergy. But rates of naturally outgrowing food allergies will vary depending on the specific food allergen and the person.

What are the symptoms of food intolerance?

Symptoms of food intolerance include:

Managing a severe food reaction with epinephrine

Shellfish is among the most common food allergens.

But every food allergies can be dangerous.

Epinephrine is the first-line treatment for anaphylaxis, a severe whole-body allergic reaction that causes symptoms, including tightening of the airway. Anaphylaxis can happen within seconds or minutes of exposure to the allergen, can worsen quickly, and can be deadly.

Once a food allergy diagnosis is made, your allergist likely will prescribe an epinephrine auto-injector and teach you how to use it. Check the expiration date of your auto-injector, note the expiration date on your calendar and enquire your pharmacy about reminder services for prescription renewals.

Be certain to own two doses available, as the severe reaction may recur.

Epinephrine should be used immediately if you experience severe symptoms such as shortness of breath, repetitive coughing, feeble pulse, generalized hives, tightness in the throat, trouble breathing or swallowing, or a combination of symptoms from diverse body areas such as hives, rashes or swelling on the skin coupled with vomiting, diarrhea or abdominal pain. Repeated doses of epinephrine may be necessary.

If you are uncertain whether a reaction requires epinephrine, use it correct away, because the benefits of epinephrine far outweigh the risk that a dose may not own been necessary.

Common side effects of epinephrine may include temporary anxiety, restlessness, dizziness and shakiness.

What are the symptoms of a shellfish allergy

Rarely, the medication can lead to an abnormal heart rate or rhythm, a heart attack, a sharp increase in blood pressure and fluid buildup in the lungs, but these adverse effects are generally caused by errors in dosing which is unlikely to happen with use of epinephrine autoinjectors. Some people with certain pre-existing conditions might be at higher risk for adverse effects and should speak to their allergist about epinephrine use.

Your allergist will provide you with a written emergency treatment plan that outlines which medications should be istered and when (note that between 10 and 20 percent of life-threatening severe allergic reactions own no skin symptoms).

Be certain you understand how to properly and promptly use an epinephrine auto-injector.

Once you own used your epinephrine auto-injector, immediately call 911 and tell the dispatcher that you used epinephrine and that more may be needed from the emergency responders.

Other medications, such as antihistamine and corticosteroids, may be prescribed to treat mild symptoms of a food allergy, but it is significant to note that there is no substitute for epinephrine — this is the only medication that can reverse the life-threatening symptoms of anaphylaxis.

How can you tell the difference between an allergy and intolerance to food?

Food allergies can be triggered by even a little quantity of the food and happen every time the food is consumed.

People with food allergies are generally advised to avoid the offending foods completely. On the other hand, food intolerances often are dose related; people with food intolerance may not own symptoms unless they eat a large portion of the food or eat the food frequently. For example, a person with lactose intolerance may be capable to drink milk in coffee or a single glass of milk, but becomes ill if he or she drinks several glasses of milk. Food allergies and intolerances also are diverse from food poisoning, which generally results from spoiled or tainted food and affects more than one person eating the food. Your health care provider can assist determine if you own an allergy or intolerance, and establish a plan to assist control symptoms.

What are the symptoms of a food allergy?

Symptoms of a food allergy can range from mild to severe, and the quantity of food necessary to trigger a reaction varies from person to person.

Symptoms of a food allergy may include:

Anaphylaxis is a extremely serious and potentially fatal allergic reaction that involves a sudden drop in blood pressure, loss of consciousness and body system failure.

How common are food allergies and intolerances?

Food allergies affect about 1 percent of adults and 7 percent of children, although some children outgrow their allergies. Food intolerances are much more common. In fact, almost everyone at one time has had an unpleasant reaction to something they ate. Some people own specific food intolerances.

Lactose intolerance, the most common specific food intolerance, affects about 10 percent of Americans.

Managing shellfish allergies in children

Because shellfish allergy reactions, love other food allergy symptoms, can develop when a kid is not with his or her parents, parents need to make certain that their child’s school, day care or other program has a written emergency action plan with instructions on preventing, recognizing and managing these episodes in class and during activities such as sporting events and field trips.

If your kid has been prescribed an auto-injector, be certain that you and those responsible for supervising your kid understand how to use it.

This sheet was reviewed and updated as of 2/13/2019.

What is a food allergy?

A food allergy is an immune system response. It is caused when the body mistakes an ingredient in food — generally a protein — as harmful and creates a defense system (antibodies) to fight it. An allergic reaction occurs when the antibodies are battling an "invading" food protein.

The most common food allergies are shellfish, nuts, fish, eggs, peanuts, and milk.

What is food intolerance?

Food intolerance is a digestive system response rather than an immune system response. It occurs when something in food irritates a person’s digestive system or when a person is unable to properly digest, or break below, the food. Intolerance to lactose, which is found in milk and other dairy products, is the most common food intolerance.

What causes food allergies and intolerances?

Food allergies arise from sensitivity to chemical compounds (proteins) in food, even compounds that are found naturally in food.

Food allergies are more common in people whose family members own allergies, suggesting a genetic — or hereditary — factor may be involved with the development of food allergies.

Food allergies develop after you are exposed to a food protein that your body thinks is harmful. The first time you eat the food containing the protein, your immune system responds by creating specific disease-fighting antibodies (called immunoglobulin E or IgE).

What are the symptoms of a shellfish allergy

When you eat the food again, it triggers the release of IgE antibodies and other chemicals, including histamine, in an effort to expel the protein "invader" from your body. Histamine is a powerful chemical that can affect the respiratory system, gastrointestinal tract, skin or cardiovascular system.

The allergy symptoms you own depend on where in the body the histamine is released. If it is released in the ears, nose and throat, you may own an itchy nose and mouth, or trouble breathing or swallowing. If histamine is released in the skin, you may develop hives or a rash. If histamine is released in the gastrointestinal tract, you likely will develop stomach pains, cramps or diarrhea.

What are the symptoms of a shellfish allergy

Numerous people experience a combination of symptoms as the food is eaten and digested.

There are numerous factors that may contribute to food intolerance. In some cases — as with lactose intolerance — the person lacks the chemicals, called enzymes, necessary to properly digest certain proteins found in food. Also common are intolerances to some chemical ingredients added to food to provide color, enhance taste and protect against the growth of bacteria.

These ingredients include various dyes and monosodium glutamate (MSG), a flavor enhancer.

Substances called sulfites, which may happen naturally — as in red wines — or may be added to prevent the growth of mold, also are a source of intolerance for some people. The Food and Drug istration has banned the use of spray-on sulfates to preserve fruits and vegetables, but sulfates are still found naturally in some foods. Salicylates are a group of plant chemicals found naturally in numerous fruits, vegetables, nuts, coffee, juices, beer and wine. Aspirin also is a compound of the salicylate family.

Foods containing salicylates may trigger symptoms in people who are sensitive to aspirin. Of course, any food consumed in excessive quantities can cause digestive symptoms.

Last reviewed by a Cleveland Clinic medical professional on 05/05/2015.

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Individuals with food allergy own an overreactive immune systemtowards aparticularfood. Such a response happens due toan antibody calledIgE (Immunoglobulin E).

Individuals suffering from food allergy often own a family history ofallergies.The most common food allergens are the proteins in cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts.

The symptoms on food allergy may not depend on the quantity of allergenic food consumed and may even happen with consumption of tiny amounts. It is also significant to note that numerous allergens may cause symptoms even after they own been cooked, and even after undergoing the digestive process. On the other hand, some otherallergens, typically certain fruits and vegetables, may only cause allergies when consumed raw.

In some food groups, such as seafood andtree nuts, a phenomenon called cross-reactivity may be seen.

This implies that if an individual has an allergy to onemember of a food family, they may also beallergic to other members of the same food group. Interestingly, cross-reactivitymay not be as commonly seen infoods from animal groups. For example, it has been found that individuals who may own allergiesto cow’s milk may still be capable toeat beef. Similarly, individuals with egg allergies may still be abletoeat chicken. It has also been found thatamong shellfish, crustaceans (shrimp, crab and lobster) are most likely to cause an allergic reaction. Other mollusks such as clams, oysters and scallops are somewhat lesscommonly associated with allergies.

Symptoms of Food Allergies:
Symptoms of allergic reactions are commonly dermatological in nature and may causeskin itching, hives and swelling.

Vomiting and diarrhea are common gastrointestinal symptoms. Symptoms of the respiratory system generally happen onlyin conjunction withskin and gastrointestinal symptoms.

Severe Allergic Reactions:
Anaphylaxis is a serious allergic reaction that happens extremely quickly and needs immediate and urgent attention!The symptoms often includedifficulty in breathing, loss of consciousness and dizziness. If you noticeany of these symptoms,especially after eating, call 911 rightaway. It is imperative to seek medical care immediately (call 911). Don’t wait to see if your symptoms go away or get better on their own. Without immediate treatment and effective and expert medical care, anaphylaxis can be lethal.

It is essential to follow up with your allergist in such cases.

An allergist is the best qualified professional to diagnose food allergy. Your allergist will take a thorough medical history, followed by a physical examination. You may be asked about contents of the foods, the frequency, seasonality, severity and nature of your symptoms and the quantity of time between eating a food and any reaction.

Allergy skin tests may determine which foods, if any, trigger your allergic symptoms.

In skin testing, a little quantity of extract made from the food is placed on the back or arm. If a raised bump or little hive develops within 20 minutes, it indicates a possible allergy. If it does not develop, the test is negative. It is unusual for someone with a negative skin test to own an IgE-mediated food allergy.

In certain cases, such as in patients with severe eczema, an allergy skin test cannot be done.

What are the symptoms of a shellfish allergy

Your doctor may recommend a blood test. Untrue positive results may happen with both skin and blood testing.

What are the symptoms of a shellfish allergy

Food challenges are often required to confirm the diagnosis. Food challenges are done by consuming the food in a medical setting to determine if that food causes a reaction.

Another question that is commonly asked is whether children outgrow their food allergies. It has been reported that most children may outgrow  certain allergies such as those to soy, egg, cow’s milk, and wheat allergy, even if they own a history of a severe reaction.

What are the symptoms of a shellfish allergy

About 20% of children with peanut allergy will outgrow it. About 9% of children with tree nut allergy will outgrow it. Your allergist can assist you study when your kid might outgrow a food allergy.


The best way to treat food allergy is to avoid the foods that trigger your allergy. Always check the ingredients when eating, especially when out of home. Carefully read labels that indicate food information.

Carefully read food labels. Always carry and know how to use injectable epinephrine and antihistamines to treat emergency reactions.

Teach family members and other people shut to you how to use epinephrine! It is also significant to wear an ID bracelet that describes your allergy.

Food allergies can be confusing and isolating. For support, you may contact the Food Allergy & Anaphylaxis Network (FAAN) at (800) 929-4040.

(Information only; not intended to replace medical advice; adapted from AAAAI)

To prevent a reaction, it is extremely significant to avoid every shellfish and shellfish products.

Always read food labels and enquire questions about ingredients before eating a food that you own not prepared yourself.

Most people who are allergic to one group of shellfish are allergic to other types. Your allergist will generally recommend you avoid every kinds of shellfish. If you are allergic to a specific type of shellfish but desire to eat other shellfish, talk to your doctor about further allergy testing.

Steer clear of seafood restaurants, where there is a high risk of food cross-contact. You should also avoid touching shellfish and going to fish markets.

Being in any area where shellfish are being cooked can put you at risk, as shellfish protein could be in the steam.

Shellfish is one of the eight major allergens that must be listed on packaged foods sold in the U.S., as required by federal law.

Avoid foods that contain shellfish or any of these ingredients:

  1. Prawns
  2. Barnacle
  3. Krill
  4. Lobster (langouste, langoustine, Moreton bay bugs, scampi, tomalley)
  5. Crawfish (crawdad, crayfish, ecrevisse)
  6. Crab
  7. Shrimp (crevette, scampi)

Your doctor may advise you to avoid mollusks* or these ingredients:

  1. Squid (calamari)
  2. Clams (cherrystone, geoduck, littleneck, pismo, quahog)
  3. Periwinkle
  4. Sea urchin
  5. Sea cucumber
  6. Cuttlefish
  7. Abalone
  8. Scallops
  9. Octopus
  10. Oysters
  11. Cockle
  12. Mussels
  13. Limpet (lapas, opihi)
  14. Snails (escargot)
  15. Whelk (Turban shell)

*Note: The federal government does not require mollusks to be fully disclosed on product labels.

Shellfish are sometimes found in the following:

  1. Seafood flavoring (e.g., crab or clam extract)
  2. Bouillabaisse
  3. Glucosamine
  4. Fish stock
  5. Cuttlefish ink
  6. Surimi

Treatment could be improved

“Active” treatment options that would desensitize shellfish-allergic patients are unfortunately not yet available.

Patients are recommended to avoid shellfish that trigger symptoms, educated to read food labels to avoid accidental consumption, take antihistamines to alleviate mild symptoms, and use epinephrine auto-injector – a hand-held device that delivers epinephrine to relax the airways by intramuscular injection – in case of an anaphylactic reaction. However, none of these first-line measures cures the disease.

Food desensitisation and tolerance induction could be achieved by “re-educating” the immune system through giving little doses of the offending food and increasing it over time.

However, existing interventions own reservations and limitations: the efficacy in developing tolerance is debatable; the adherence of patients is poor as the treatment is lengthy (2 to 5 years to “complete”); there are risks such as developing allergic side effects; and they’re costly, running between US$800 and $1,000 per year.

Our research team therefore focused our effort to address these shortcomings through investigating the worth of peptide-based oral immunotherapy, by which these peptides are short fragments of tropomyosin with molecular nature of modifying the immune system, and also by constructing hypoallergens of shrimp tropomyosin and hypoallergen-based vaccines. Hypoallergens are modified from tropomyosin to be less than normally allergenic.

What is shellfish allergy?

Shellfish allergy is a type of hyper-immune response mediated by Immunoglobulin E (IgE), an antibody produced by B cells.

When someone who is allergic eats some shellfish, the allergens – primary tropomyosin, a muscle protein – bind with IgE.

This allergen-IgE complicated then cross-links on mast cells. These cells frolic a key role in the inflammatory process, by which they contain numerous granules wealthy in inflammatory mediators love histamine. Histamine can increase the permeability of the blood capillaries, exert effects on mucous glands and bronchila tubes, and is a central mediator of allergic reactions love itching.