Shrimp allergy (IgE shrimp)

Shrimp belong to the crustaceans, as do crab, lobster and crayfish; crustaceans must be listed as an allergen on food packaging. Symptoms can come from eating, but also from touching, from breathing in steam while crustaceans are being cooked, or from oil containing traces of crustaceans. This test measures the amount of IgE antibodies against the proteins in shrimp in the blood, in kU/l. The body only makes these antibodies after it has previously been in contact with the allergen; this is called sensitization. Other crustaceans and mollusks, such as mussels, are not measured separately.

• Sensitization to shrimp: the body has made IgE antibodies against shrimp
• Support in working out a suspected allergy to shrimp, together with the history of the symptoms
• Support in answering whether a reaction after eating, touching or cooking shrimp fits an allergy

The GP mainly looks at the history: which symptoms, when and where they occur and after contact with what. With a positive result and matching symptoms, advice usually follows to limit contact with the allergen and, if needed, medication. With a severe reaction, in case of doubt or with symptoms that are not brought under control this way, a referral to an allergist, pediatrician, ENT specialist or lung specialist may follow.

A positive IgE result shows sensitization, not allergy: it only says that there are antibodies, not that you get symptoms from them. The Dutch medical specialists' guideline (FMS) on upper airway allergy says this literally and recommends choosing a test for single allergens based on the history of the symptoms; for food allergy, the FMS guideline on food challenge testing calls the history of the symptoms the cornerstone of diagnosis and a food challenge in hospital the gold standard. The result therefore only means something if it fits when, where and after contact with what you get symptoms. A positive result without symptoms is not treated.

• Sensitization without symptoms is common; the result can only be interpreted together with the history of the symptoms.
• Related allergens can recognize each other's antibodies (cross-reaction), for example pollen and nuts or fruit; a positive result then does not mean that this particular allergen causes the symptoms.
• The test measures all proteins from the allergen source together; testing for individual proteins (components) can say more in case of doubt.
• Laboratories use different measurement methods and cut-off values; results from different labs cannot be compared one to one.

According to Stichting Voedselallergie, about 1 in 100 people have an allergy to fish or crustaceans. Crustacean allergy is most common in adults and, after peanut and nuts, is the most common cause of a severe allergic reaction (anaphylaxis). Someone who has a crustacean allergy will probably not outgrow it.

Useful with a clear reaction after eating, touching or cooking shrimp or other crustaceans, such as itching and swelling in the mouth and throat, hives, vomiting or shortness of breath; symptoms usually start within an hour. In people with a house dust mite allergy who eat shrimp normally, the result can be positive due to cross-reaction without a shrimp allergy. In people who eat shrimp without symptoms, the test adds nothing.

• NVKC, allesovertesten.nl: Allergie (RAST)
• FMS Richtlijnendatabase: Allergie van de bovenste luchtwegen, module Aanvullende diagnostiek
• FMS Richtlijnendatabase: Voedselprovocatie, module Plaatsbepaling diagnostiek voedselallergie
• Thuisarts.nl: Ik heb allergie
• NHG-Standaard Voedselovergevoeligheid en coeliakie (M47)
• Stichting Voedselallergie: Schaaldieren
• Thuisarts.nl: Ik denk dat ik niet tegen bepaald voedsel kan