How common is a seafood allergy?
The prevalence of seafood hypersensitivity strongly depends on the region and the proportion of such products in the diet [1]. Global estimates suggest that people with this type of allergy may account for as much as 2.5% of the population [2]. It is worth noting here that seafood is not only oysters and shrimps. There are three subgroups: fish, molluscs and crustaceans [3].
How can an allergy to frutti di mare manifest itself?
Symptoms after eating seafood can appear within minutes, but also after a longer period of time. These include nausea, vomiting, hives or shortness of breath. It is important to note that seafood can also cause generalised symptoms, i.e. anaphylaxis [4]. They can also cause anaphylactic shock, which is a life-threatening condition for the allergic person.
What can a reaction to seafood be caused by?
Unfortunately, discovering the correct cause of a reaction to fish and other marine animals is not that simple. The reason for the symptoms is not always an allergy.
Cross-reactions also occur with seafood. A cross-reaction occurs when an organism that is allergic to protein ‘A’ mistakes it for a very similar protein ‘B’. The immune system then reacts to the other molecule as a result of some kind of confusion [5]. The molecules Pen m 1 of a shrimp, Hel as 1 of a snail, Cra g 1 of an oyster, Per v 1 of a clam are among the proteins that cross-react with… Der p 10 of house dust mites! Although they are, at first glance, completely different organisms, they share a certain protein in common, which is tropomyosin. It is this muscle-building molecule of different organisms that is ‘confused’ by our immune system [6].
A second potential cause of an allergic reaction to seafood is the nematode Anisakis simplex, a small parasite. It is tempting to say that nobody enjoys them for lunch or dinner. Unfortunately, we can still be exposed to them. According to a 2004 study, more than 80% of coastal herring in the Baltic Sea may be infected with this parasite [7]! This poses a risk to other fish that are found in the same environment and, of course, to consumers. Most of the allergens of the nematode Anisakis simplex are thermostable. This means that even after frying or baking fish contaminated with larvae, an allergic reaction can occur [8].
Selected seafood allergens
The vast majority of allergenic proteins in seafood belong to the same group – tropomyosins. They are found in the muscles of many organisms, such as house dust mites, cockroaches, snails, various types of oysters, lobsters and crabs. Unfortunately, an allergy to these particles is associated with a high risk of a severe anaphylactic reaction. However, this is not the end of the bad news. Tropomyosin’s are thermostable, which means that they are allergenic even when fried, cooked or baked. Another characteristic of these molecules is their very similar structure.
In which organisms are tropomyosins found that an allergic person should watch out for?
- House dust mite: Der p 10, Der f 10, Aca s 10
- Anisakis simplex nematode: Ani s 3
- Snail: Hel as 3
- Shrimp: Lit v 1, Pen m 1,
- Cockroach: Per a 7
- Calamari: Uro du 1
- Crab: Can p 1, Cha f 1, Cra c 1
- Clam: Ven ga 1 [9, 10].
Sylwia Gałązka
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translation: Julia Majsiak
Updated 23.08.2023
Publication 05.08.2023
