Anisakis simplex: what is it?

Anisakis simplex

Anisakis simplex: what is it?

An allergy to seafood such as shellfish is common, but it isn’t always that simple. There’s a small chance that something else might be the cause of your allergic reaction, known as anisakis simplex. Although this can make individuals suffer from symptoms similar to food poisoning, it can induce allergic responses in others. The infection itself is called anisakiasis, or herring worm disease.

What is it?

Simply put, anisakis is a parasitic worm that infects marine fish and shellfish, but unfortunately, through our consumption of seafood, it can go on to infect people too, known as anisakiasis. A common parasite in fish, cases of anisakiasis in humans have increased over the last 50 years. It has been more frequent in Japan where raw fish consumption is high.

The infections can happen when we eat the fish, causing inflammation in parts of the body including the oesophagus, stomach, or intestine. The easiest way to avoid it is to stop eating fish altogether, but that isn’t likely to happen. Restaurants with high food hygiene ratings are more likely to be safer, so do your research before you dine out.


Along with those mentioned above, several symptoms can suggest you might have a case of anisakiasis, including:

  • Hives
  • Abdominal pain
  • Nausea or vomiting

Individuals may also experience a tickling or tingling sensation in their mouth, and possibly the throat, after eating fish; this is a sign that the worm itself may still be in your mouth. Coughing this up before swallowing may help to prevent infection.


Sometimes it can cause allergic reactions. It can be difficult to diagnose an anisakis allergy as people will confuse it with a seafood allergy. Any allergic reaction should be treated seriously as it can lead to anaphylaxis. If this is the case, seek help immediately. Avoiding seafood might be a suitable solution if you suffer from the symptoms after eating seafood, even if not caused by the simplex.

If you react to a fish you’ve eaten before, this could be a sign of anisakis allergy. Alternatively, you may have developed a late on-set allergy to fish or histamine poisoning. Histamine is sometimes present in fish such as tuna or mackerel, and the symptoms are similar to fish or simplex allergies.

If you think you have the condition, it’s critical to visit your GP to ensure that you don’t suffer from long-term effects such as small bowel obstruction.

Although you can find anisakis simplex in countries such as Japan who consume large amounts of raw fish, it is also present in the UK. Indeed, it has been reported in five different continents.

To prevent fish allergies or simplex infections, it is critical to avoid consuming poorly cooked fish, shellfish, and squid. We highly recommend being tested for allergies to take further precautions.

Request an allergy test from us today to put you on the right path to living allergy free. Don’t risk critical side effects like anaphylaxis, contact us today for more information to find out how we can help you.

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