Allergy to crustaceans and molluscs

Mussels and shrimps are often lumped together – also conceptually. Mostly they are called shellfish. The following actually applies: mussels, snails and cephalopods such as squid are mollusks. Shrimps, lobsters, crayfish and lobsters belong to the phylum of arthropods; more precisely to the subgenus of crustaceans. In the kitchen crustaceans, which can be eaten, are often called crustaceans.


In Europe react about 0.1 percent of people in so-called provocation tests allergic to crustaceans and / or mollusks. Countries where a lot of seafood is consumed have higher allergy rates. In Scandinavia, Portugal and Spain, crustacean and mollusk allergies are among the most common food allergies.

Molluscs and crabs


Main allergens in crustaceans and mollusks are so-called Tropomyosins. These proteins are important for muscle movements. Since they are not destroyed by heat, both raw and cooked crustacean and mollusk meat can cause allergies.

While the allergy usually occurs when the crustaceans or mollusks are eaten, it can be enough for sensitive people to inhale the steam of cooked seafood. Skin contact can also cause allergic reactions. Above all in the fishery or in the catering trade this form of the sensitization plays a role.

Allergy can be to individual crustacean species as well as to several species of crustaceans. The same is true for the mollusk species. In some cases, those affected are allergic to cancer- and Mollusks allergic and can not tolerate any of the seafood.

By the way, some people with a Dust mite allergy also an allergy to crustaceans and molluscs. The reason: house dust mites, like crustaceans, belong to the phylum of arthropods and have tropomyosins. If sufferers are already sensitized to these dust mite tropomyosins, their immune system also recognizes the similarly structured proteins of crustaceans and mollusks as dangerous. In addition to the dust mite allergy, there is also the food allergy. Sometimes this also happens in reverse order (after a cancer or mollusc allergy, a dust mite allergy develops).


Crab and mollusk allergies can cause mild but also severe allergic reactions in various organs: from the so-called oral allergy syndrome, in which the mucous membrane in the mouth and throat tingling or swelling for a few minutes to hours after ingestion, up to and including anaphylactic shock with respiratory distress and circulatory arrest.

It can lead to abdominal pain, vomiting or diarrhea come. Also the Skin skin may become red, itchy, or form wheals. In some cases the Respiratory involved. Symptoms range from allergic rhinitis to asthmatic symptoms.

Childhood allergy to crustaceans and mollusks

Allergies to crustaceans and mollusks can develop as early as infancy. It is assumed that in Europe about 0.1 percent of all children are affected. While food allergies to milk or egg often subside, studies suggest that crustacean and mollusk allergies usually persist for a lifetime.

Diagnostic procedures

The doctor first clarifies whether a cancer and/or mollusc allergy is present in an Conversation about dietary habits and complaints.

The suspicion of an allergy will be skin and/or blood test further confirmed. These tests indicate an allergic disposition to a certain substance, but they cannot prove an allergy. Therefore, when in doubt, another diagnostic procedure is used: The Provocation test. For this, the affected person eats an allergen-free diet for some time. Then, under medical supervision, small amounts of cancer or molluscum are administered to them. Mollusk protein administered. In this way it can be checked whether and which of the animals are actually allergenic or whether they can be removed from the list of suspicious substances.

From the symptoms of a crab and mollusk allergy complaints must be delineated, which are allergy-like, but are caused by bacteria, viruses or toxins in the sea animals. For example, microalgae in mollusks can produce toxins that mimic an allergic reaction.


A crab and mollusk allergy is most effectively relieved by treating the Triggers avoided are. The allergist can only decide which animals should be removed from the diet after a thorough diagnosis.

People with a severe crustacean and/or mollusk allergy, in which even the smallest amounts of protein trigger an anaphylactic shock, must have an emergency kit consisting of an adrenaline autoinjector, a corticosteroid (liquid or tablet) and an antihistamine (liquid or tablet).

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