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Cross-reactivity: when one allergy comes with another

Why an allergy to one food or pollen can bring reactions to related foods, and where research finds that this is common and where it is rare.

4 minute read11 sources, each checked word for wordLibrary checked October 16, 2026

In short

  • Some proteins are shared across plants (such as profilin and lipid transfer proteins) and animals (such as tropomyosin and caseins). This sharing is how cross-reactions happen.Review1
  • Peanut and tree nut allergy occur together in about a third of children with peanut allergy.E2Good2
  • Clinically important cross-reactions among legumes are very rare in children.E2Good3
  • Pollen food allergy syndrome is usually mild and limited to the mouth, but severe reactions are possible.E2Good4,5

How sure each claim is:E1StrongE2GoodOfficial textReviewWhat the grades mean

What is cross-reactivity?

A number of allergy-causing proteins are conserved across related plants and animals. Examples are profilin and lipid transfer proteins in plants, and tropomyosin and caseins in animals.Review1

A clinician deciding about related foods weighs a careful history, lab tests and, in some cases, oral food challenges.Review1

With cross-reactive proteins, false-positive skin and blood tests are a bigger problem than usual. So a positive test to a related food does not by itself show a reaction will happen.Review1

Peanut, tree nuts and other legumes

In children with peanut allergy, tree nut reactions occurred in about one third, often on the first known exposure, and could be life-threatening.E2Good2

Among children who reacted to tree nuts, the most common were walnut, almond and pecan.E2Good2

Peanut is a legume, like soy, peas and beans. Food challenges showed that clinically important cross-reactivity among legumes is very rare in children. The authors concluded that a reaction to one legume does not warrant removing all of them. They added that skin tests alone should not set long-term restrictions.E2Good3

Milk, fish and shellfish

In children with IgE-mediated cow's milk allergy, 24 of 26 also reacted to goat's milk in blinded challenges. The authors concluded goat's milk is not a suitable substitute.E2Good6

All 30 fish-allergic patients in one study had IgE to parvalbumin, a protein found across six fish species. This makes parvalbumin a cross-reactive fish allergen.E2Good7

Shellfish include mollusks and crustaceans; shrimp cause most crustacean reactions. Tropomyosin, arginine kinase and several other proteins are the most relevant shellfish allergens.Review8

Pollen and fresh fruits, vegetables and nuts

In older children, teenagers and adults, a substantial part of all IgE-mediated food allergy comes from structures shared between pollens (or other inhaled allergens) and foods.E2Good9

This is called pollen food allergy syndrome. British nut allergy guidelines describe it as usually mild, with symptoms in the mouth and throat in people with hay fever. They add that it is usually distinguishable from a primary nut allergy.E2Good4

Reported rates range from 4.7% to over 20% in children and 13% to 58% in adults.Review5

Symptoms usually stay in the mouth because the proteins break down easily. But some proteins are more stable, and anaphylactic shock has been documented in up to 1.7% of reactions.Review5

For this reason a review concluded it cannot be dismissed as a harmless food allergy.Review5

Reactions can happen the first time a food with a cross-reactive protein is eaten. Component testing may help with diagnosis, and an unclear history may need a supervised challenge.E2Good9

Latex and fruit

In one group of people with latex allergy, 52% also had allergies to certain fruits, which the authors called the latex-fruit syndrome. The most frequent were avocado, chestnut, banana, kiwi and papaya.E2Good10

Red meat and mammal products

In alpha-gal syndrome, blood tests found IgE to beef, pork, lamb, cow's milk, cat and dog, but not to turkey, chicken or fish.E2Good11

Alpha-gal has its own guide: Alpha-gal syndrome and red meat.

What is not known yet

Which cross-reactions matter for one person cannot be read from a list. Reviews stress careful history, lab tests and, in some cases, food challenges for each person.Review1

Questions you might bring to your clinician

  1. Which related foods have actually caused reactions, and which only showed up on a test?
  2. Is this pattern more like pollen food allergy syndrome or a primary food allergy?
  3. Would component testing or a supervised challenge help sort out a related food?
  4. Are there related foods that do not need to be avoided?

Every claim in this guide was written from its sources and checked against them word for word. Its clinical review by Dr. Recio, whose specialty is anesthesia, is pending; an allergist has not yet reviewed it. This line changes when each review is done.

Sources

Each source opens on PubMed, DailyMed or the publisher's page. Under each one are the exact words from it that this page relies on, copied word for word and checked against the original.

  1. Clinical implications of cross-reactive food allergens. Sicherer SH, J Allergy Clin Immunol, 2001. Review Expert review
    The words this page rests on
    A variety of these allergens conserved among plants (eg, profilin and lipid transfer proteins) and animals (eg, tropomyosin and caseins) have been characterized.
    The physician is called on to determine the risk of reaction to related foods among legumes, tree nuts, fish, shellfish, cereal grains, mammalian and avian food products, and a variety of other plant-derived foods that may share proteins with pollens, latex, and each other. Clinical evaluations require a careful history, laboratory evaluation, and in some cases oral food challenges.
    The pitfalls in the evaluation of food allergy-unreliable histories and limitations in laboratory assessment primarily caused by false-positive skin prick test responses/RAST results are magnified when dealing with cross-reactive proteins.
  2. Clinical features of acute allergic reactions to peanut and tree nuts in children. Sicherer SH, Pediatrics, 1998. E2Good Observational study
    The words this page rests on
    PN and TN allergic reactions coexist in one third of PN-allergic patients, frequently occur on first known exposure, and may be life-threatening, requiring emergency treatment.
    Of those reacting to TN, 34 had reactions to one, 12 to two, and 8 to three or more different TN, the most common being walnut, almond, and pecan.
  3. Cross-allergenicity in the legume botanical family in children with food hypersensitivity. Bernhisel-Broadbent J, J Allergy Clin Immunol, 1989. E2Good Observational study
    The words this page rests on
    Results of oral food challenges demonstrate that clinically important cross-reactivity to legumes in children is very rare. Clinical hypersensitivity to one legume does not warrant dietary elimination of all legumes. Results of prick skin tests should not be used to determine prolonged food restriction diets.
  4. BSACI guideline for the diagnosis and management of peanut and tree nut allergy. Stiefel G, Clin Exp Allergy, 2017. E2Good Guideline
    The words this page rests on
    Pollen food syndrome is a distinct disorder, usually mild, with oral/pharyngeal symptoms, in the context of hay fever or pollen sensitisation, which can be triggered by nuts. It can usually be distinguish clinically from primary nut allergy.
  5. Pollen food allergy syndrome (PFAS): A review of current available literature. Carlson G, Ann Allergy Asthma Immunol, 2019. Review Expert review
    The words this page rests on
    Commonly these reactions are limited to the oropharynx due to the lability of the proteins causing the reaction. As multiple families of proteins with varying stability cause PFAS, severe systemic reactions are also possible, as anaphylactic shock has been documented in up to 1.7% of reactions.
    Varying reports have been made of the prevalence of PFAS, ranging from 4.7% to greater than 20% in children and 13% to 58% in adults.
    Pollen food allergy syndrome therefore cannot be dismissed as a benign food allergy, but it needs to be approached individually based on known risk factors.
  6. Allergenicity of goat's milk in children with cow's milk allergy. Bellioni-Businco B, J Allergy Clin Immunol, 1999. E2Good Observational study
    The words this page rests on
    All the children had positive skin test responses and CAP results to both CM and GM, all had positive DBPCOFC results to CM, and 24 of 26 had positive DBPCOFCs to GM.
    These data strongly indicate that GM is not an appropriate CM substitute for children with IgE-mediated CMA.
  7. Parvalbumin, a cross-reactive fish allergen, contains IgE-binding epitopes sensitive to periodate treatment and Ca2+ depletion. Bugajska-Schretter A, J Allergy Clin Immunol, 1998. E2Good Observational study
    The words this page rests on
    Sera from all patients allergic to fish (n = 30) displayed IgE reactivity to parvalbumin, a 12 kd protein present in fish extracts from six different species.
    Parvalbumin represents a cross-reactive fish allergen.
  8. Shellfish allergens: tropomyosin and beyond. Faber MA, Allergy, 2017. Review Expert review
    The words this page rests on
    Shellfish are classified into mollusks and crustaceans, the latter belonging to the class of arthropoda. Among crustaceans, shrimps are the most predominant cause of allergic reactions and thus more extensively studied.
    Among them, invertebrate tropomyosin, arginine kinase, myosin light chain, sarcoplasmic calcium-binding protein, and hemocyanin are the most relevant.
  9. Position paper of the EAACI: food allergy due to immunological cross-reactions with common inhalant allergens. Werfel T, Allergy, 2015. E2Good Consensus statement
    The words this page rests on
    In older children, adolescents, and adults, a substantial part of all IgE-mediated food allergies is caused by cross-reacting allergenic structures shared by inhalants and foods.
    Local, mild, or severe systemic reactions may occur already after the first consumption of a food containing a cross-reactive allergen.
    Component-resolved diagnosis may help to reach a diagnosis and may predict the risk of a systemic reaction. Allergy needs to be confirmed in cases of unclear history by oral challenge tests.
  10. Latex allergy: clinical features and cross-reactivity with fruits. Blanco C, Ann Allergy, 1994. E2Good Observational study
    The words this page rests on
    The most frequent food hypersensitivities were to avocado (9), chestnut (9), banana (7), kiwi (5) and papaya (3). Through RAST-inhibition, cross-reactivity among latex, avocado, chestnut, and banana was demonstrated.
    Our data suggest the existence of a "latex-fruit syndrome," because 52% of our latex allergic patients had allergies to certain fruits.
  11. Delayed anaphylaxis, angioedema, or urticaria after consumption of red meat in patients with IgE antibodies specific for galactose-alpha-1,3-galactose. Commins SP, J Allergy Clin Immunol, 2009. E2Good Observational study
    The words this page rests on
    CAP-RAST testing revealed specific IgE antibodies to beef, pork, lamb, cow's milk, cat, and dog but not turkey, chicken, or fish.