Allergy cross-reactivity occurs when your immune system reacts to proteins in one substance that resemble proteins in another. Understanding which allergens share cross-reactive proteins helps you anticipate unexpected food reactions. Search below by allergen name or food item to find related allergen groups and risk levels.
Birch Pollen (Bet v 1 protein)
50-70% cross-reactivityLatex (Hev b proteins)
30-50% cross-reactivityRagweed Pollen
10-50% cross-reactivityCrustacean Shellfish (Tropomyosin)
75%+ within crustaceansGrass Pollen
10-30% cross-reactivityDust Mites
Rare — documented cross-reactivityRisk Level Guide
How to Use the Allergy Cross-Reactivity Guide
This allergy cross-reactivity guide helps you identify foods and substances that may cause reactions due to shared protein structures with your known allergens. Use the search box to quickly find allergens or foods, or browse the full groups below.
Understanding Cross-Reactivity
When your immune system creates IgE antibodies against one allergen, it may also recognize structurally similar proteins in other substances. The degree of cross-reactivity depends on how similar the proteins are at the molecular level. Some cross-reactions are well-documented and predictable; others are rare and highly individual.
The Most Important Groups
The most clinically significant cross-reactive groups are: birch pollen with stone fruits and nuts (very common in northern climates); latex with banana, avocado, and kiwi (latex-fruit syndrome); crustacean shellfish with other shellfish (high-risk for anaphylaxis); and ragweed with melons and cucumbers.
When to Suspect Cross-Reactivity
Consider cross-reactivity if you develop oral tingling or symptoms shortly after eating certain fruits, vegetables, or nuts — especially if you have known seasonal allergies. Symptoms that progress beyond the mouth (hives, throat tightness, breathing difficulty) require immediate evaluation and possible epinephrine use.
Getting Tested
An allergist can perform skin prick tests or specific IgE blood tests to identify cross-reactive sensitivities. Component testing (measuring IgE to specific proteins like Bet v 1) provides the most precise cross-reactivity profile. This helps distinguish between genuine cross-reactive sensitization and coincidental results.
FAQ
Is this allergy guide free?
Yes, completely free with no signup required. All information runs locally in your browser.
Is this a substitute for medical advice?
No. This is an educational reference guide only. Allergy cross-reactivity varies greatly between individuals. Always consult a board-certified allergist for diagnosis and management of food or environmental allergies. Severe reactions (anaphylaxis) require emergency medical care.
What is allergy cross-reactivity?
Cross-reactivity occurs when proteins in one substance are structurally similar to proteins in another. Your immune system may recognize both as the same allergen, causing reactions to foods or substances you have not directly been sensitized to. For example, if you are allergic to birch pollen, you may also react to apples and hazelnuts because they share similar proteins.
What is oral allergy syndrome?
Oral allergy syndrome (OAS) is a common cross-reactive condition where pollen-allergic individuals experience mild tingling or itching in the mouth and throat when eating certain raw fruits, vegetables, or nuts. Unlike true food allergy, OAS symptoms are usually limited to the mouth and resolve quickly. Cooking the food often breaks down the cross-reactive proteins, eliminating the reaction.
What is latex-fruit syndrome?
Latex-fruit syndrome occurs in people with latex allergy who may also react to certain fruits. The proteins in latex are structurally similar to proteins in banana, avocado, kiwi, and chestnut, with 30-50% cross-reactivity. People with confirmed latex allergy should discuss latex-fruit syndrome with their allergist.
Can I eat shrimp if I am allergic to crab?
Shellfish cross-reactivity is very high within crustaceans (shrimp, crab, lobster, crawfish) at 75%+ cross-reactivity. If you are allergic to one crustacean, you are highly likely to react to others. Cross-reactivity with mollusks (clams, oysters, scallops) is lower at 30-50%. Consult your allergist before eating any shellfish if you have a confirmed shellfish allergy.
How reliable are these cross-reactivity percentages?
Cross-reactivity rates are based on published allergy research and immunological studies. They represent population-level probabilities, not guarantees for any individual. Some people with birch allergy have no issues with apples; others have significant reactions. Individual testing with an allergist determines your specific cross-reactive profile.
What does 'high', 'medium', and 'low' risk mean?
High risk (75%+) means the majority of people with the primary allergen will also react. Medium risk (30-60%) means reactions are common but not universal. Low risk (10-30%) means reactions occur in a significant minority. These estimates apply to IgE-mediated (immediate) allergic reactions.