By Dr. Hilary Booth, ND
This summer, we’re seeing many people suffering from allergies. It’s not uncommon that patients have been tested for allergies with their MD, so they know which allergens are triggering their symptoms. This test, known as the “scratch test” or “skin prick test”, involves introducing a small amount of each allergen to the skin, usually the forearm. If the skin becomes red and inflamed, you know you’re allergic to those allergens.
Many patients test positive for environmental allergens like grass, pollen, birch, dust, and pet dander, and despite trying to avoid these things, they still often experience allergy symptoms. Did you know that many foods cross-react with these environmental allergens, making allergy symptoms worse?
What is cross-reactivity?
When our body is exposed to a foreign substance, it creates a specific immune response to find and attack that substance. Our immune systems are constantly doing this to protect us from bacteria, viruses, and environmental intruders including dust, pollens, and foods.
People with environmental allergies have become “sensitized” for their immune systems to react to certain triggers, such as ragweed. When the immune system is exposed to the allergen, it creates a huge histaminic response resulting in itching, watery eyes, runny nose, and sinus congestion: aka allergies.
The problem is that sometimes the immune system gets confused, and this is where cross-reactivity comes into play. When the immune system detects certain markers on some foods (profilin and lipid transfer protein), it mistakes them for markers on our environmental allergens. So by complete accident, the immune system mounts that itchy histaminic response to the food instead of to the environmental trigger.
The good news is that we can use this knowledge of cross-reactivity to our advantage to help improve our seasonal allergies by simply avoiding the foods that cause the immune system to react.
Interestingly, the markers profilin and lipid transfer proteins are often de-stabilized by cooking, so it’s the raw versions of these foods that we need to avoid.
1. Birch tree pollen sensitivity
Many hay-fever sufferers are allergic to birch tree pollen. The most commonly experienced symptom of food cross-reactivity with birch tree pollen is called oral allergy syndrome, seen in about 40% of people allergic to birch. Oral allergy syndrome is local throat and lip itching that happens within a few minutes of eating a birch-cross-reacting food. This is different from an anaphylactic reaction, which would involve swelling of the throat and mouth needing emergency intervention. The itching can be mildly irritating, only happens when we eat raw versions of these foods, and usually subsides on its own.
If you do experience oral allergy syndrome or have a birch tree allergy, consider eliminating raw versions of the following foods:
- Fruits: Apple, cherry, pear, plum, peach, nectarine, kiwi
- Veggies: fennel, parsnip, carrot, onion, potato, tomato, celery, spinach
- Nuts: hazelnut, walnut, peanut
- Grains: wheat, buckwheat
- Other: honey (pollen)
2. Grass pollen sensitivity
If you experience environmental allergies caused by grass, you may consider eliminating raw versions of the following foods to reduce symptoms caused by cross-reactivity. These do not cause oral allergy syndrome as described above.
- Melon, orange, Swiss chard tomato, watermelon, wheat
3. Ragweed pollen sensitivity
If you experience environmental allergies caused by ragweed, you may consider eliminating raw versions of the following foods to reduce symptoms caused by cross-reactivity. These do not cause oral allergy syndrome as described above.
- Banana, honey, melon, cantaloupe, zucchini, artichoke, sunflower seeds, honey
- Herbs/teas: chamomile, Echinacea, hibiscus, milk thistle, goldenseal
4. Latex sensitivity
Although latex allergies aren’t thought of as traditional environmental allergies, I thought it worth noting in this article that people who experience contact sensitivity to latex products can have a severe allergic reaction to these cross-reactive foods. If you do have a latex allergy, it is strongly recommended that you get blood tests done for anaphylactic reactions to the following foods.
- Most common: avocado, banana, kiwi, chestnut
- Other possible cross-reactive foods: apricot, celery, dandelion, grapes, mango, melon, papaya, passion fruit, peach, pineapple, spinach, sunflower, tomato