What are the signs of shellfish allergies

What are the signs of shellfish allergies

Anaphylaxis is a medical emergency. It can be extremely serious if not treated quickly.

If someone has symptoms of anaphylaxis, you should:

  • Lie the person below flat – unless they’re unconscious, pregnant or having breathing difficulties.
  • Call 999 for an ambulance immediately (even if they start to feel better) – mention that you ponder the person has anaphylaxis.
  • Remove any trigger if possible – for example, carefully remove any stinger stuck in the skin.
  • Use an adrenaline auto-injector if the person has one – but make certain you know how to use it correctly first.
  • Give another injection after 5 to 15 minutes if the symptoms do not improve and a second auto-injector is available.

If you’re having an anaphylactic reaction, you can follow these steps yourself if you feel capable to.

Read about how to treat anaphylaxis for more advice about using auto-injectors and correct positioning.

If you’re having an anaphylactic reaction, you can follow these steps yourself if you feel capable to.

Read about how to treat anaphylaxis for more advice about using auto-injectors and correct positioning.


Treatment could be improved

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

What are the signs of shellfish allergies

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.

What are the signs of shellfish allergies

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.


A lifelong condition

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.

What are the signs of shellfish allergies

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.

What are the signs of shellfish allergies

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.

What are the signs of shellfish allergies

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.

What are the signs of shellfish allergies

To study more about this author’s research, visit her dedicated sheet on the AXA Research Fund website.

Anaphylaxis is a severe and potentially life-threatening reaction to a trigger such as an allergy.


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.

What are the signs of shellfish allergies

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.


Symptoms of anaphylaxis

Anaphylaxis generally develops suddenly and gets worse extremely quickly.

The symptoms include:

There may also be other allergy symptoms, including an itchy, raised rash (hives); feeling or being sick; swelling (angioedema) or stomach pain.


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