Food and Environmental Allergen Cross-Reactivities

IgE-mediated immune reactions (allergies) to foods can cause reactions ranging from severe anaphylaxis to mild nasal congestion. The onset of most food allergies is within 15 minutes, meaning that the offending food is usually quickly identified, particularly in a severe reaction. Mild reactions may be a little more difficult to pinpoint, particularly when different foods are consumed together. Food sensitivities (an IgG-mediated reaction) tend to be even more difficult to identify because the onset of symptoms can take up to 72 hours to manifest, and may present very differently than IgE reactions. Brain Fog, lack of energy, cramping, chronic skin issues, and other conditions that could have many etiologies are all possible with food sensitivities.

Environmental allergens, such as pollen from grasses, weeds, and trees; molds, pet dander, dust mites, and material from household pests tend to be airborne allergens rather than ingested. This often means that watery eyes and nasal or throat irritation can be present and immediately identify an environmental allergy, especially because there is a fairly rapid onset like food allergies. Identifying exactly which allergen is triggering the reaction, though, may be difficult because exposure is often passive rather than active. 

An additional complicating factor in identifying a particular allergen, be it food or environmental, is the possibility of cross-reactivity. The immune system can react to a potential allergen that it is not primed to react to because the proteins in that substance resemble the proteins in an allergen that the immune system is primed to react to. This can be because the two substances are in the same family, and/or share a similar protein structure. Cross-reactivities within the same food families are fairly well known. For instance, a patient who has an allergy to one species of crustaceous shellfish may very well be allergic to another species of crustaceous shellfish. Other reactions can fall outside of food families. Peanuts are a legume, but there can be cross-reactivity between peanut and tree nut allergies, even though those foods are not in the same family. Cross-reactivity can also occur between food allergens and environmental allergens. In fact, there are a whole range of these cross-reactivities. Here are some of the major ones to be aware of (note- these lists are not exhaustive but include the major players):

Pollen Food Allergy Syndrome (PFAS) Also known as Oral Allergy Syndrome (OAS), is a cross-reactivity between common pollens and fruits, nuts, grasses, and vegetables. This is usually triggered when someone with an existing pollen allergy then consumes food that shares a similar protein structure to the pollen. These cross-reactive allergies can be rapid, or more systemic in nature. They are more often found with raw foods than with cooked foods, but depending on the person, both could cause problems. PFAS is best understood as a cluster of food allergy cross-reactivities as there are specific pollens that can interact with a variety of foods.

• Birch pollen- 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, and beans

• Alder pollen-  Apple, cherry, peach, pear, strawberry, raspberry, celery, parsley, hazelnut, almond, and walnut

• Grass pollen- Fig, melon, orange, kiwi, watermelon, tomato, potato and peanut

• Mugwort pollen- Mango, celery, and carrot

• Ragweed pollen- Banana, watermelon, honeydew, cantaloupe, squash, pepper, cucumber, artichoke, hibiscus, zucchini, chamomile, and sunflower
  
  

Latex Allergies Patients who have latex allergies may react to certain fruits and tubers that have similar protein structures to latex. The most common is a cross-reactivity to banana, but those with latex allergies might also react to avocado, kiwi, peach, plum, fig, grapes, melons, papaya, passion fruit, cherries, nectarines, pears, pineapple, strawberries, carrots, celery, raw potatoes, cassava/manioc, tomatoes, chestnuts, hazelnuts, wheat, and rye. As you can see, even though it is often called latex-fruit syndrome, foods other than fruits can be involved.

Crustacean Allergies As mentioned previously, there can commonly be cross-reactions between different species of crustaceans for patients allergic to one of them. In addition, there are environmental/food cross-reactivities possible between crustacean allergies and allergies to cockroaches or dust mites. 

Alpha-gal Syndrome (AGS) AGS is transmitted by tick bites and causes an allergy to galactose-α-1,3-galactose, a carbohydrate that is found in all non-primate mammals. The allergy has been most strongly associated with the Lone Star Tick, but is thought to possibly be associated with other ticks as well. The allergy can be mild or very severe, even life-threatening, and is potentially triggered by consuming any meat from mammals after a tick bite. Research is emerging at this fairly recently identified allergy. The CDC believes that over 100,000 patients may be affected by previous tick bites. 

Mold Allergies Those who are affected by environmental mold allergies can also be allergic to mold in foods as well as to candida and yeasts. These include foods that intentionally use molds, such as some cheeses, cured meats, and kombucha; and products with yeasts such as fermented foods, breads and cakes, and wine, cider, mead, and beer. It can also include food and drinks that are contaminated by molds or yeasts. 

Other Meat Allergies Meat allergies can sometimes be cross-reactive with pets. Dog and cat dander may cross-react with beef and/or pork, or with goat or cow’s milk. Allergies to bird feathers or down may be cross-reactive to chicken, turkey, or eggs. 

The Precision Point P88 Dietary Antigen Test tests for IgE, IgG, IgG4, and Complement to 88 foods and conveniently groups them in food families to easily see potential food family cross-reactions. The P88 DAT also includes yeast, mold, and candida in the panel.