Resources for Medical Professionals
Learn more about common allergic diseases, symptoms, management paradigms, and testing considerations.
Is your patient a candidate for specific IgE testing?
Get detailed information on whole allergens and allergen components.
Ready to test a patient?
Access videos and webinars delivered by key experts in the field of allergy.
Resources for Medical Professionals
Learn more about common allergic diseases, symptoms, management paradigms, and testing considerations.
Is your patient a candidate for specific IgE testing?
Get detailed information on whole allergens and allergen components.
Ready to test a patient?
Access videos and webinars delivered by key experts in the field of allergy.
What is allergy cross-reactivity?
March 2026 | ✓ Medically Reviewed by: Gary Falcetano, PA-C, AE-C
Allergy cross-reactivity occurs when the body's immune system identifies the proteins in one substance (e.g., pollen) and the proteins in another (e.g., a fruit or vegetable) as being similar.1 When an individual comes into contact with either, whether or not it’s a protein in something that he or she is truly allergic to, the immune system can react in the same way, which in some cases can cause allergic symptoms.
All that matters to the immune system is that the proteins are structurally similar or biologically related. If they are, cross-reactivity can occur. The risk of allergy cross-reactivity needs to be assessed by a healthcare professional. The potential for cross-reactivity can make diagnosing specific allergies somewhat complicated.2
Symptoms that have manifested as a result of cross-reacting antibodies (i.e., proteins produced by the immune system to fight disease) cannot always be distinguished from those caused by genuine sensitization. However, by determining the primary sensitization, treatment or avoidance of symptoms can be effective.
What is Pollen Food Allergy Syndrome (PFAS)?
Pollen Food Allergy Syndrome (PFAS), also known as Oral Allergy Syndrome (OAS), is an allergic reaction that typically occurs after a patient who is sensitive to pollen eats certain foods, e.g., fruits, vegetables, nuts, and grains.3 PFAS is possibly the most common food allergy in adults, with up to 60 percent of patients allergic to pollen being affected.3 Additionally, up to 25 percent of children with allergic rhinitis (i.e., hay fever) also suffer from OAS. 4
If you're sensitized to pollen, you may experience PFAS when certain foods touch your oral mucosa (the tissue lining the inside of your mouth), lips, tongue, or throat. The symptoms of OAS appear within minutes of eating a raw form of the food but can last for hours. In the majority of cases, the responsible allergens are rapidly denatured by cooking and digestion, though certain patients can still present with systemic reactions.3
PFAS cross-reactivity allergy list
People with Oral Allergy Syndrome (OAS) typically have an allergy to birch trees, ragweed, or grass pollen.5 Foods that may cause OAS include tree nuts, soy, peanut, fruits, and vegetables.5
Pollen
Fruits
Vegetables
Nuts
Grains
Birch
Kiwi, apple, pear, plum, peach, nectarine, apricot, cherry, banana, fig, avocado, strawberry, dried plum, mango
Celery, carrot, parsnip, parsley, dill, cumin, cilantro, fennel, potato, tomato, pepper (green), chicory
Hazelnut, almond, walnut, peanut
Soy, wheat, lentils, peas, beans
Alder
Apple, cherry, peach, pear, strawberry, raspberry
Celery, parsley
Hazelnut, almond, walnut
Grass
Fig, melon, orange, kiwi, watermelon
Tomato, potato
Peanut
Mugwort
Mango
Celery, carrot
Ragweed
Banana, watermelon, melon, honeydew, cantaloupe
Squash, pepper, cucumber, artichoke, hibiscus, zucchini, chamomile tea
Sunflower seeds
Other types of cross-reactivity
Cross-reactivity between shellfish:1 There is a high degree of cross-reactivity among crustacean shellfish (e.g., shrimp, lobster, crab, crawfish). The risk may be lower for cross-reactivity between crustacean shellfish and non-crustacean shellfish (mollusks) such as clams, oysters, scallops, and mussels. Of note, there is cross-reactivity between chitins (a component of the exoskeleton of shellfish and insects) in dust mites and crustacean shellfish in the form of a cross-reactive risk protein called tropomyosin.
Cross-reactivity between latex and food:1 Approximately 30 to 70 percent of people with IgE-mediated allergies to latex can experience symptoms with any of several fruits cross-reactive to latex, including most commonly banana, avocado, kiwi, and chestnut. Several types of proteins have been identified to be involved in Latex-Fruit Syndrome.
Cross-reactivity between peanut and tree nuts or seeds: Peanut and tree nut allergies are often characterized by life-threatening anaphylactic reactions and lifelong persistence. While peanut allergy is more commonly seen in patients, many subjects develop a hypersensitivity to both peanuts and tree nuts.6 Although peanuts are actually legumes, approximately 20 to 30 percent of those with a peanut allergy are also allergic to one or more types of tree nuts.7 Additionally, walnut, pecan, and hazelnut comprise a group of strongly cross-reactive tree nuts. Hazelnut, cashew, Brazil nut, pistachio, and almond form another group of moderately cross-reactive tree nuts.8
Cross-reactivity between cats and other animals: It might seem like common sense, but there is a high degree of cross-reactivity between one of the proteins found in cats that is also found in dogs.9 Maybe a little more surprising is that cat allergens also can cross-react with some horse allergens.10 And there also is allergen cross-reactivity between cats and pigs. Pork-Cat Syndrome is a rare allergic reaction to a protein that’s found in both cat dander and pork, and being sensitized to this protein in cats can cause a person to have allergic symptoms when they consume pork.11
What is cross-contact?
Cross-contact happens when a small amount of allergen gets into a food that it shouldn’t be in. Some food labels include “may contain” or “processed in the same facility as” identifiers due to cross-contact. When it comes to food allergies, it’s important to understand the difference between cross-contact and cross-reactivity to avoid confusion and/or an unnecessary reaction.
Diagnosing cross-reactivity: What your provider will look for
One way to help get to the bottom of what’s causing your symptoms is to talk with your healthcare provider about a specific IgE blood test. It's a diagnostic test that uses just one blood draw and can test from among a selection of hundreds of potential allergic triggers. The results of a blood test with allergen components, along with a detailed medical history and a physical examination, will help your provider determine your specific allergen triggers. Once your provider has determined if it’s the pet, pollen, or peanuts that are causing your symptoms (or all three), they can help develop a customized treatment plan.
Tools for Understanding Allergies
Track allergy symptoms and prepare for a visit with a healthcare provider.
Learn about specific allergens, including common symptoms, management, and relief.
Are you a healthcare provider? Get comprehensive information on hundreds of whole allergens and allergen components.
- Matricardi PM, Kleine-Tebbe J, Hoffmann HJ, Valenta R, Hilger C, Hofmaier S, Aalberse RC, Agache I, Asero R, Ballmer-Weber B, Barber D, Beyer K, Biedermann T, Bilò MB, Blank S, Bohle B, Bosshard PP, Breiteneder H, Brough HA, Caraballo L, Caubet JC, Crameri R, Davies JM, Douladiris N, Ebisawa M, EIgenmann PA, Fernandez-Rivas M, Ferreira F, Gadermaier G, Glatz M, Hamilton RG, Hawranek T, Hellings P, Hoffmann-Sommergruber K, Jakob T, Jappe U, Jutel M, Kamath SD, Knol EF, Korosec P, Kuehn A, Lack G, Lopata AL, Mäkelä M, Morisset M, Niederberger V, Nowak-Węgrzyn AH, Papadopoulos NG, Pastorello EA, Pauli G, Platts-Mills T, Posa D, Poulsen LK, Raulf M, Sastre J, Scala E, Schmid JM, Schmid-Grendelmeier P, van Hage M, van Ree R, Vieths S, Weber R, Wickman M, Muraro A, Ollert M. EAACI Molecular Allergology User's Guide. Pediatr Allergy Immunol. 2016 May;27 Suppl 23:1-250. doi: 10.1111/pai.12563. PMID: 27288833.
- American Academy of Allergy, Asthma & Immunology [Internet]. Milwaukee, WI: American Academy of Allergy, Asthma & Immunology; 2021. Available from: https://www.aaaai.org/tools-for-the-public/allergy,-asthma-immunology-glossary/cross-reactivity-defined.
- Kashyap RR, Kashyap RS. Oral Allergy Syndrome: An Update for Stomatologists. J Allergy. 2015;2015:543928.
- Roberts, Graham & Xatzipsalti, M & Borrego, Luis & Custovic, Adnan & Halken, Susanne & Hellings, Peter & Papadopoulos, Nikolaos & Rotiroti, G & Scadding, Glenis & Timmermans, Frans & Valovirta, Erkka. (2013). Pediatric rhinitis: Position paper of the European Academy of Allergy and Clinical Immunology. Allergy. 68. 10.1111/all.12235.
- American College of Allergy, Asthma & Immunology [Internet]. Arlington Heights, IL: American College of Allergy, Asthma & Immunology; 2019 Mar 21.
- De Leon MP, Glaspole IN, Drew AC, Rolland JM, O'Hehir RE, Suphioglu C. Immunological analysis of allergenic cross-reactivity between peanut and tree nuts. Clin Exp Allergy. 2003 Sep;33(9):1273-80. doi: 10.1046/j.1365-2222.2003.01761.x. PMID: 12956750.
- McWilliam V, Koplin J, Lodge C, Tang M, Dharmage S, Allen K. The Prevalence of Tree Nut Allergy: A Systematic Review. Curr Allergy Asthma Rep. 2015 Sep;15(9):54. doi: 10.1007/s11882-015-0555-8. PMID: 26233427.
- Goetz DW, Whisman BA, Goetz AD. Cross-reactivity among edible nuts: double immunodiffusion, crossed immunoelectrophoresis, and human specific igE serologic surveys. Ann Allergy Asthma Immunol. 2005 Jul;95(1):45-52. doi: 10.1016/S1081-1206(10)61187-8. PMID: 16095141.
- Liu Z, et al. Albumins represent highly cross-reactive animal allergens. Frontiers in Immunology. 2023;14:1241518.
- Todorović N, et al. Major Cat Allergen Fel d 4: Structure and Identification of a Cross-Reactive IgE-Epitope-Containing Area. Allergy. 2025.
- Kim C, et al. Recurrent urticaria caused by specific cat serum albumin IgE cross-reacting with pork serum albumin. Clinical and Experimental Pediatrics. 2020;63(11):451-453.
Thank you for visiting Allergy Insider
Before you go, we'd appreciate your feedback to help us better understand your needs and improve our services.
Create a summary of your allergy symptoms in a downloadable document
Share the summary with your healthcare provider for a productive conversation about allergy blood testing
Gain an optimized diagnosis and a personalized treatment plan
Allergy Symptom Questionnaire
Allergies affect us all differently. This questionnaire will summarize your specific allergy symptoms to share with your healthcare provider and learn more about your testing options.
- Create a summary of your allergy symptoms in a downloadable document
- Share the summary with your healthcare provider for a productive conversation about allergy blood testing
- Gain an optimized diagnosis and a personalized treatment plan
|
Create a summary of your allergy symptoms in a downloadable document |
Create a summary of your allergy symptoms in a downloadable document
|
Share the summary with your healthcare provider for a productive conversation about allergy blood testing |
Share the summary with your healthcare provider for a productive conversation about allergy blood testing
|
Gain an optimized diagnosis and a personalized treatment plan |
Gain an optimized diagnosis and a personalized treatment plan
Purchase the same tests your doctor orders and get insights into your health. Our convenient allergy tests can measure your immune response to common allergies found in the air, in foods and with pets.
Buy your own allergy tests online, anytime. Test for 15 common food allergens and up to 25 common indoor and outdoor respiratory allergens. The same quality lab tests doctors use and recommend, but no doctor visit required for purchase.
Get quality care on your schedule. Our board-certified providers can perform an exam, evaluate your symptoms, and test you for allergies to create a personalized treatment plan.
You are now leaving thermofisher.com and going to a site owned and operated by an independent third party. Thermo Fisher Scientific is not responsible or liable for any content or services of any independent third-party site. Thermo Fisher Scientific does not represent independent third parties or the customer if the two enter into a transaction. Privacy and security policies on these sites may differ from those practiced by thermofisher.com. We encourage you to review the policies and terms of all websites you may choose to visit.
You are now leaving thermofisher.com, and going to ondemand.labcorp.com, owned and operated by an independent third party. Thermo Fisher Scientific is not responsible or liable for any content or services of ondemand.labcorp.com. Thermo Fisher Scientific does not represent either Labcorp OnDemand or the customer if the two enter into a transaction. Privacy and security policies of ondemand.labcorp.com may differ from those practiced by thermofisher.com. We encourage you to review the policies and terms of all websites you may choose to visit.
WE’RE HERE TO HELP
Stop wondering, start testing
Get science-backed answers to your allergy questions. Test your body’s immune response to indoor and outdoor allergens like dust and pollen, dog and cat dander and saliva, or to common food allergy triggers including lactose, shellfish and nuts.
- Purchase your test at ondemand.labcorp.com using a credit card or FSA/HSA
- Schedule an appointment at one of our 2,000+ locations to collect your sample
- Get your results quickly online in 2-4 days
VISIT QUESTHEALTH.COM
Health insights you can act on
Get insights about your health, when you want them. Test for 15 common food allergens and up to 25 common indoor and outdoor respiratory allergens. You will have the option to discuss your results with an independent physician at no extra cost.
- Visit questhealth.com to purchase your allergy test, no doctor visit required
- Schedule your appointment at a Quest location near you
- Access your results from your phone as soon as they are available
You are now leaving thermofisher.com and going to questdiagnostics.com owned and operated by an independent third party. Thermo Fisher Scientific is not responsible or liable for the content or services of questdiagnostics.com. Thermo Fisher Scientific does not represent either Quest Diagnostics or the customer if the two enter into a transaction. Privacy and security policies of questdiagnostics.com may differ from those practiced by thermofisher.com. We encourage you to review the policies and terms of all websites you may choose to visit.
MINUTECLINIC AT CVS
We’re here when you need us
High quality and affordable health care is available on your schedule. Our board-certified providers can perform an exam, evaluate your symptoms, and test you for allergies to create a personalized treatment plan.
Appointments available in-person and virtually 7 days a week, including evenings
- Schedule online, in-person or in the CVS Pharmacy App
- Affordable out of pocket costs
- Most insurance plans accepted
You are now leaving thermofisher.com, and going to cvs.com/minuteclinic, owned and operated by an independent third party. Thermo Fisher Scientific is not responsible or liable for the content or services of cvs.com/minuteclinic. Thermo Fisher Scientific does not represent either MinuteClinic at CVS or the customer if the two enter into a transaction. Privacy and security policies of cvs.com/minuteclinic may differ from those practiced by thermofisher.com. We encourage you to review the policies and terms of all websites you may choose to visit.