Shrimp and Prawn Allergy Cross-Reactivity
If you are allergic to shrimp, you will almost certainly be allergic to prawns, as they are both crustaceans sharing the same major allergen (tropomyosin) with extremely high cross-reactivity rates of 50-100% for sensitization and 38% for clinical reactions. 1
Understanding the Cross-Reactivity
Tropomyosin is the primary culprit responsible for cross-reactivity between shrimp and prawns. This protein is a highly conserved panallergen found across all crustacean species, making allergic reactions predictable across this food group 1. The molecular structure of tropomyosin remains remarkably similar between different crustacean species, which is why your immune system cannot distinguish between shrimp and prawns 2.
Key Allergens Involved
- Tropomyosin is the major allergen with a molecular weight of 31-38 kDa, appearing consistently in immunoblotting studies of both shrimp and prawns 1, 2
- Arginine kinase (40 kDa) represents another cross-reactive panallergen found in prawns, lobster, crab, and other crustaceans 1
- These proteins are so stable and conserved that they maintain their allergenic properties even after cooking 1
Clinical Evidence for Cross-Reactivity
The data strongly supports near-universal cross-reactivity:
- 50-100% sensitization rate between shrimp and other crustaceans (including prawns) 1
- 38% clinical reactivity rate when exposed to different crustacean species 1
- Laboratory studies demonstrate IgE antibodies from shrimp-allergic patients bind to prawn proteins at the same molecular weight bands 2, 3
- Mouse models confirm that shrimp sensitization produces IgE that is cross-reactive with other crustaceans 4
Critical Clinical Implications
You should avoid all crustaceans, not just shrimp. This includes:
- Prawns (essentially the same risk as shrimp)
- Lobster
- Crab
- Crayfish
- Any other crustacean species 1
The greatest number of anaphylactic episodes in adults is due to shellfish, making this a potentially life-threatening allergy. 1
Important Caveats
Mollusks Are Different
Cross-reactivity between crustaceans (shrimp/prawns) and mollusks (clams, oysters, scallops) is much lower:
- Only 47% sensitization rate 1
- Only 14% clinical reactivity rate 1
- While some cross-reactivity exists due to shared tropomyosin, many shrimp-allergic patients can tolerate mollusks 2
Testing Limitations
Do not assume you can eat prawns based on the absence of a prior reaction. Clinical cross-reactivity studies show that 38% of patients with documented shrimp allergy will react to other crustaceans even without prior exposure 1. The first exposure to prawns after developing shrimp allergy could be the first severe reaction.
Diagnostic Approach
If confirmation is needed:
- Skin prick testing to both shrimp and prawn extracts can demonstrate cross-reactivity 1, 2
- Serum-specific IgE testing will typically show positive results to both species 2, 3
- Immunoblotting can reveal identical IgE-binding protein bands (typically 36-38 kDa) for both shrimp and prawns 2
- Oral food challenges should never be performed outside a medical facility with personnel prepared to treat anaphylaxis 1
Management Recommendations
Carry two epinephrine autoinjectors at all times and avoid all crustaceans, including prawns 5. The risk of severe anaphylaxis with crustacean allergies is substantial, and reactions can be fatal 1.
Arrange follow-up with an allergist-immunologist for comprehensive evaluation, formal testing, and development of an anaphylaxis emergency action plan 5.