Fish and shellfishf351

Tropomyosin allergy (Pen a 1)

Pen a 1 is tropomyosin from shrimp, the most important allergen in shellfish allergy. IgE to Pen a 1 suggests that you may react to several kinds of shellfish and sometimes to mites.

Allergen
Tropomyosin (Pen a 1) Penaeus aztecus
Allergen code
f351
Key allergens
Pen a 1
Included in
1 test
Contents
  1. What is Pen a 1?
  2. What does the result mean?
  3. Symptoms of shellfish allergy
  4. Cross-reactivity
  5. How to get tested
  6. Frequently asked questions

What is Pen a 1?

Pen a 1 is a single protein, tropomyosin, from shrimp. An ordinary allergy test for shrimp measures IgE to the whole shrimp, whereas a component test such as Pen a 1 shows which protein you react to. Tropomyosin is a muscle protein that withstands heat and resembles tropomyosin in other crustaceans, molluscs, mites and cockroaches.

What does the result mean?

  • IgE to Pen a 1 suggests that you may react to several kinds of shellfish, such as shrimp, prawns, crab, lobster and crayfish. It can also explain a simultaneous allergy to mites or cockroaches.
  • IgE to shrimp but not to Pen a 1 can mean that you react to other proteins in the shrimp. The result then needs to be interpreted together with your symptoms.

Symptoms of shellfish allergy

  • Itching and swelling in the mouth and throat
  • Hives
  • Vomiting and stomach ache
  • Breathing difficulties and, in rare cases, anaphylaxis

Cross-reactivity

Because tropomyosin is so similar between species, IgE to Pen a 1 can cause reactions to many kinds of shellfish. The same protein is found in house dust mites and cockroaches, and some people who first became allergic to mites later react to shellfish.

How to get tested

Tropomyosin Pen a 1 (allergen code f351) is included in our Shellfish allergy test, together with shrimp. The combination shows whether you have IgE both to shrimp as a whole and to its tropomyosin.

Frequently asked questions

What is a component test?

A component test measures IgE to a single protein instead of the whole allergen source. It gives a more detailed picture of what you react to and helps your doctor assess the risk of cross-reactions.

Do I have to avoid all shellfish if I have IgE to Pen a 1?

It is common to be advised to avoid shellfish, but the assessment should be made by a doctor based on your symptoms and test results.

Often cross-reacts with

This text is general information and does not replace an assessment by a healthcare professional. In an emergency, call 112. If you have questions about your health, contact your doctor.

Tests for tropomyosin allergy (Pen a 1)

You take the sample yourself at home. The tests measure IgE antibodies in a capillary blood sample.

Fish and shellfish

Fish and shellfish allergies often last a lifetime. People who react to one type of fish often react to several, because the most important proteins are similar.

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