If I am allergic to shrimp, can I eat crab or lobster?

Shellfish Allergy Cross-Reactivity: Risk of Crab and Lobster Consumption in Shrimp-Allergic Individuals

If you are allergic to shrimp, you should avoid eating crab and lobster due to the high risk of cross-reactivity between crustacean shellfish species. 1

Understanding Shellfish Allergy Cross-Reactivity

Shellfish allergies involve two main groups:

1. Crustaceans: Shrimp, crab, lobster, crawfish
2. Mollusks: Clams, mussels, oysters, scallops, squid, octopus

The primary reason for cross-reactivity between different crustaceans is tropomyosin, a muscle protein that functions as a major allergen across invertebrate species:

• Tropomyosin is highly conserved among crustaceans with significant sequence identity 2
• This protein creates a "pan-allergen" effect, causing allergic reactions across multiple shellfish species 2
• Studies have demonstrated immunological relationships between crustaceans, showing tropomyosin as the common major allergen 2

Evidence Supporting Avoidance of All Crustaceans

Clinical evidence strongly supports avoiding all crustaceans if you have a shrimp allergy:

• Cross-reactivity between different fish species is common but not universal, however, cross-reactivity between crustacean shellfish species (shrimp, crab, lobster) is particularly high 1
• Patients with shellfish-induced allergic reactions should strictly avoid all shellfish from their specific group (crustaceans or mollusks) 1
• Research has shown that individuals with shrimp allergy often have positive skin tests and RAST (radioallergosorbent test) results to other crustaceans even without prior exposure to those specific shellfish 3

Risk of Severe Reactions

The potential severity of allergic reactions makes avoidance crucial:

• Shellfish allergies can trigger anaphylaxis, a potentially life-threatening reaction 4
• Severe food reactions can involve multiple body systems including gastrointestinal, cutaneous, respiratory, and cardiovascular 4
• Even minimal exposure can trigger reactions - one documented case showed anaphylaxis occurring after a kiss from someone who had recently consumed shellfish 5

Diagnostic Considerations

If you want to determine the exact extent of your shellfish allergy:

• Skin prick testing and serum-specific IgE testing can help identify cross-reactivity patterns 1
• Oral food challenges are the gold standard but must be performed in a medical facility by personnel experienced in treating anaphylaxis 1
• These tests can potentially identify safe alternative seafood species if any exist for your specific case 1

Management Recommendations

For individuals with confirmed shrimp allergy:

1. Avoid all crustacean shellfish (shrimp, crab, lobster, crawfish) due to high cross-reactivity 1
2. Carry an epinephrine auto-injector if you have a history of severe reactions 1
3. Read food labels carefully and inform restaurants about your allergy 1
4. Be aware of potential cross-contamination in food preparation areas 1
5. Consider testing for mollusks separately, as cross-reactivity between crustaceans and mollusks is possible but less consistent 1

Important Distinction

While there is high cross-reactivity among crustaceans, it's worth noting:

• There is no significant cross-reactivity between fish (e.g., salmon, tuna) and shellfish allergies 1
• Patients allergic to shellfish can typically consume finned fish unless separately allergic to both 1
• Shellfish allergy has no relationship to iodine or iodinated contrast media allergy 1

In conclusion, the scientific evidence strongly supports avoiding crab and lobster if you have a confirmed shrimp allergy due to the high likelihood of cross-reactivity and potential for serious allergic reactions.