Up to 60 percent of all food reactions occur because of cross-reactions between food and pollen. A great example is birch pollen cross-reacts with hazelnuts, apples, celery, carrot, soy, and countless other foods. So, what happens when a patient that has been doing well on their food elimination diet comes into the clinic and says, "it stopped working, my symptoms are back"? The answer may be as simple as the change of seasons and thus change in pollen counts. A patient may be able to modestly tolerate a given food until Spring, Summer, or Autumn arrives. This article and accompanying webinar will help identify and demystify confounding variables.
For instance, about 50 to 60 percent of people who are allergic to latex also have "latex-fruit syndrome," where they develop adverse reactions after consuming cross-reacting vegetables and fruits, including bananas, avocados, chestnuts, kiwis, chickpeas, and bell peppers.
There is even some growing evidence that non-pollen related cross-reactions include Candida's association with yeast and gluten-containing foods cross-reacting with coffee, dairy, oats, and yeast.
When the allergy season arrives, many patients are focused on avoiding pollen from trees and grasses. Yet, they're not aware of an important fact—if they're reacting to tree and grass pollen, they are also likely reacting to specific foods as well. If they're eating those foods simultaneously as they're suffering from hay fever, they're only going to make their pollen-related allergies worse.
Immunological Double Exposure
Most food allergies in adolescents and adults are acquired due to cross-reaction to pollen allergens.1 These pollen allergens are found in various fruits and vegetables, causing many pollen-allergic patients to develop many different plant food allergies.1 They may even react to foods they've never eaten before.1
As stated at the beginning of this article, adults, up to 60 percent of food-allergic reactions occur because of cross-reactions between food and pollen.2
The family of lipid-transfer proteins (LTP) is also responsible for the cross-reactivity between many foods and pollen. LTPs also responsible for the systemic symptoms in food allergy patients.3 Researchers have identified allergens from this family in most vegetables and fruits.3
Seventy-five percent of patients who suffer from peach allergy recognize the peach LTP, known as Pru p 3, which is to blame for food cross-reactivities—especially those related to fruits and nuts—as well as pollens from mugwort and plane trees.4
Knowing which foods cross-react with pollen sources is critical for diagnosing patients and improving the treatment of their sensitivities and allergies.5
In the Western developed world, birch pollen allergy is the form of allergic rhinitis most likely to be accompanied by food allergies. Up to 80 percent of people who suffer from birch pollen allergies also have food allergies.6
Chances are good that if someone is allergic to birch pollen, they'll also react to hazelnuts and apples, which are the most common allergenic foods in this group of people.7
Usually, when a food allergy is related to birch pollen, patients experience mild allergic symptoms, such as oral contact urticarial, when they consume allergenic foods. The symptoms are usually confined to the oral cavity and can include swelling and itching of lips, tongue, soft palate, and pharynx.6-8
Seventy to 95 percent of birch pollen allergic patients also develop allergic reactions to the celery or carrot's allergens. Celery can cause anaphylactic reactions in persons allergic to mugwort and birch pollen. This cross-reaction occurs even though the birch allergen Bet v 1 and the celery allergen Api g 1 have only a 40 percent amino acid sequence similarity.8-10
Soy can also cause problems, and some birch-pollen allergic patients have gone into anaphylaxis after exposure to soy.8
For many people, birch-related food allergies don't go away when allergy season is over. Most experience food-related symptoms outside the birch pollen season, indicating that homologous food allergens cause a continual increase in birch-pollen-specific immune responses.8
Common Cross-Reactions Between Pollen and Food
Birch pollen: apple, carrot, celery, pear, tomato, cherry, tree nuts.
Goosefoot pollen: banana, melon, peach (infrequently: nectarine, asparagus, kiwi, potato, olive, onion).
Mugwort pollen (weed): carrot, celery, aniseed, peach.
Ragweed pollen: melon, cucumber, banana, sunflower, echinacea.
Timothy grass: apple, litchi, tomato, celery, corn, bell pepper, paprika.
Allergy to latex is common and well-known. About 50 to 60 percent of people who are allergic to latex also have "latex-fruit syndrome," where they develop adverse reactions after consuming cross-reacting vegetables and fruits.11
The most common foods to cross-react with latex are bananas, avocados, chestnuts and kiwis.12 Latex also cross-reacts with chickpeas13 and bell peppers.14
In a study reported in 2004, researchers found that the major latex allergen Hev b 2 and the bell pepper l-ascorbate peroxidase are cross-reactive allergens. The researchers also showed that profilins are responsible for some of the IgE cross-reactivity.14
Latex Cross-Reactivity With Fruits and Vegetables
||Banana, Avocado, Chestnut, Kiwi
||Apple, Carrot, Celery, Papaya, Potato, Tomato, Melons
|Low or Undetermined
||Pear, Mango, Sweet Pepper, Plum, Wheat, Shellfish, Cherry, Hazelnut, Sunflower Seeds, Pineapple, Walnut, Citrus Fruits, Strawberry, Soybean, Coconut, Fig, Peanut, Chickpea, Grape, Buckwheat, Castor Bean, Apricot, Dill, Passion Fruit, Oregano, Zucchini, Nectarine, Sage, Persimmon
In some cases, people are allergic to latex and don't know it. A group of researchers from Japan demonstrated in a study published in 2005 that some patients showed positive reactions for tests used to determine allergy to latex (both specific IgE and the skin prick test), even though they could tolerate latex products in their daily lives. These same patients were allergic to foods that cross-react with latex.15
Olive Tree Cross-Reactivity
Olive tree (Olea europaea) pollen is a main cause of allergies in extensive areas of Europe and North America. Ole e 10, a small and acidic protein, has been identified as a major allergen from olive pollen. Ole e 10 shares IgE B cell epitopes with proteins from birch, latex, and foods such as tomato, kiwi, potato, and peach.16
Grass Pollen and Ragweed
Patients allergic to grass pollen are known to have adverse reactions to plant foods such as peanuts, garlic, tomatoes, potatoes, green peas, watermelon, melon, apple, orange, kiwi, onion, and peach.17-18 They can also react to animal foods such as egg whites and pork.17
Researchers have also discovered an association between ragweed pollinosis and hypersensitivity to cucurbitaceae vegetables (watermelon, melon, cucumber) and bananas.18
Ragweed also cross-reacts with echinacea, which may be the reason why a small number of people develop severe allergic reactions after consuming echinacea.19-20
Non-Pollen Related Cross-Reactions
Pollen isn't the only substance that cross-reacts with food. Candida albicans is known to cross-react with the yeast Saccharomyces cerevisiae. In a study published in 1997, researchers also tested the sera of 349 patients with allergies who were positive for IgE antibodies against C. albicans to see if the C. albicans cross-reacted with other forms of yeast. The researchers found that 41 of the 349 patients (11.7 percent) reacted with the heat extracts of all 13 yeast species tested.21
Testing and Supplemental Support
The first step is to test patients for seasonal hay fever allergies using the skin prick test. This can determine which pollens are affecting them and guide you in recommending which foods they should avoid.
Having your patients take an at-home food allergy test available from Complementary Prescriptions will also provide critical knowledge of which foods they should avoid. Some foods might not cross-react with pollen but are allergenic for other reasons. If so, these foods will weaken the body, making it more vulnerable to seasonal allergies.
To get your patients through the allergy season and beyond, it's important to treat more than just the hay fever. Determining which foods are causing cross-reactions can make a world of difference in the treatment outcome. It's also critical to explore the possibility of cross-reactivity in gluten-sensitive patients who are not experiencing improvement after avoidance of gluten-free foods.
Action Steps For Cross-Reactivity
Seasonal allergies, latex allergies, and gluten intolerance can be made worse when a patient eats foods that cross-react with pollen or gluten—testing patients for pollen allergies to determine which substances are causing their seasonal allergy symptoms. Have them avoid all foods that cross-react with the offending pollen source and, when possible, vice versa.
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- Bar-El Dadon S, et al. Food Chem. 2013 May 1;138(1):13-8.
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- [No authors listed] Consum Rep. 2012 Feb;77(2):12.
- Mullins RJ. Med J Aust. 1998 Feb 16;168(4):170-1.
- Kanbe T, et al. Clin Exp Allergy. 1997 Dec;27(12):1449-57.