Shrimp allergy

What symptoms can an IgE-mediated shrimp allergy cause?

After a reaction: document the product precisely

• Date and time, exact dish, restaurant or brand, a photo of the packaging and the ingredients list.
• Type or species of shrimp if known, raw or cooked, whole or peeled, and approximate amount.
• Delay before symptoms, precise description, medicines used, any adrenaline given and the emergency-department report.
• If the dish contained several types of seafood, list them separately instead of concluding ‘seafood allergy’.

Can I react simply by touching shrimp?

Yes, in some people, especially with repeated or occupational exposure. Handling raw shrimp can cause contact hives, itching or protein contact dermatitis. This has been described in particular in fishmongers, cooks and seafood-industry workers.

What about steam or cooking aerosols?

Smell alone is not necessarily allergenic. However, some cooking or preparation methods may disperse tiny droplets containing shrimp proteins into the air. Rhinitis or asthma has mainly been described with high exposure, particularly at work.

Can someone be ‘allergic to chitin’ in the shell?

Why is tropomyosin so important?

Tropomyosin is a highly conserved muscle protein in invertebrates and is relatively heat resistant. It is a major allergen in many crustaceans and explains some cross-reactions with other crustaceans, certain molluscs, house dust mites and cockroaches.

Shrimp ↔ house dust mites: how is this possible?

House dust mite tropomyosin, particularly Der p 10, resembles crustacean tropomyosin. A person sensitised to house dust mites may therefore have IgE that recognises shrimp without necessarily having a clinical food allergy. The same phenomenon has been described with cockroaches.

Shrimp ↔ other crustaceans

Cross-reactivity is common between shrimp, crab, lobster, langoustine, spiny lobster and crayfish, particularly because their tropomyosins are similar. However, a clinical reaction to every crustacean is not automatic: foods already eaten without a reaction provide essential information.

Shrimp ↔ molluscs

Mussels, oysters, scallops, clams, snails, whelks, squid, cuttlefish and octopus are molluscs. Cross-reactions exist, but are less predictable than between crustaceans. It is not justified to exclude every mollusc in advance for every patient allergic to shrimp.

Be careful with mixed dishes and cross-contact

• Seafood platters, paella, soups and stocks, curries, Asian sauces, sushi or maki, and dim sum.
• Shared deep fryers, the same griddle or utensils, seafood restaurants and some buffets.
• A dish containing fish and crustaceans may cause a reaction to crustaceans without indicating a fish allergy.

What about edible insects?

Tropomyosin and arginine kinase are also found in some insects such as crickets, locusts and mealworms. Cross-reactivity is biologically possible in patients sensitised to crustaceans or house dust mites, but this does not justify general avoidance without a clinical history.

What about red carmine / cochineal colouring E120?

In practice: what you tolerate also matters

Saying ‘I regularly eat salmon, mussels or crab without a problem’ is just as important as describing what caused the reaction. Once an allergy has been confirmed, current recommendations favour keeping foods shown to be tolerated in order to avoid unnecessary restrictions.

Reading labels

In European labelling, crustaceans, fish and molluscs are three separate allergen categories. ‘Contains crustaceans’ means that a crustacean is an ingredient; ‘may contain crustaceans’ is a precautionary statement relating to a risk of accidental presence. Advice about traces must be personalised.

What happens during allergy assessment?

• History: species or type of shrimp, amount, cooking method, delay, symptoms, treatment and other seafood already tolerated.
• Skin prick tests: commercial extracts and, in some centres, prick-to-prick testing with raw or cooked food when useful.
• Specific IgE: confirms sensitisation but does not, on its own, predict the severity of a future reaction.
• Molecular allergology: tropomyosin (Pen a 1 / Pen m 1) may help explain some profiles but is not sufficient to diagnose or exclude the allergy.

Shrimp oral food challenge

An oral food challenge remains the reference diagnostic test when the history is uncertain, tests are discordant, house dust mite sensitisation complicates interpretation or tolerance needs to be checked. It is performed under medical supervision with increasing doses.

What about shrimp-triggered FPIES?

Food protein-induced enterocolitis syndrome (FPIES) is a non-IgE-mediated food allergy. In adults, crustaceans and other seafood are among the most commonly reported triggers. Its presentation differs from immediate allergy: abdominal pain, nausea, repeated vomiting and/or diarrhoea, often delayed, without the hives or respiratory symptoms typical of IgE-mediated allergy.

Negative IgE + vomiting after shrimp = no allergy?

Does shrimp allergy persist?

Crustacean allergy tends to last longer than milk or egg allergy and often begins later in life. However, ‘often persistent’ does not mean ‘necessarily lifelong’: reassessment may remain appropriate depending on the history and how test results change.

What should be avoided when the allergy is confirmed?

• First, avoid the responsible shrimp and preparations containing that shrimp.
• How far avoidance should extend to other crustaceans depends on the history, foods already tolerated, tests and sometimes an OFC.
• Do not automatically remove fish or molluscs that are already tolerated solely because a shrimp allergy has been diagnosed.

Is an emergency kit needed?

Common misconceptions

Before your appointment: the SOS Allergo checklist

• Exact name of the dish, photo of the product or menu, species or type of shrimp if known, raw or cooked, amount and delay before symptoms.
• Photos of the reaction, treatments used, emergency-department report, any reaction during contact, peeling or exposure to cooking vapours.
• List of crustaceans, molluscs and fish already eaten without a problem; known allergy to house dust mites or cockroaches.