United Allergy Blog

5 interesting cases of allergic cross-reactivity

Allergy sufferers cope with their sensitivities in a number of ways, from over-the-counter medication and immunotherapy treatment to simple avoidance. Yet, even if a person was to employ every known method of avoidance, it’s still possible he or she would still experience an allergic reaction at a time when an allergen is nowhere to be seen.

The reason why is cross-reactivity, a phenomenon in which “the proteins in one substance are similar to the proteins found in another substance”. That means that a person allergic to a particular pollen may see a similar reaction after eating a nut, spice, or piece of fruit that is cross-reactive with that particular pollen.

When we consume a cross-reactive protein, the ensuing reaction is known as oral allergy syndrome. Oral allergy syndrome can be triggered by a variety of foods that many of us eat on a daily basis, resulting in mild to moderate symptoms that range from swelling and itching around the mouth to watery eyes and runny noses.

With that in mind, here are five cases of cross-reactivity to keep an eye out for the next time you’re at the grocery store.

1. Cypress pollen and peaches, citrus fruits

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A recently discovered cross-reactivity according to Science Daily, peaches and citrus fruits such as oranges have demonstrated a possibility for allergic reactions. For people with cypress allergies, that is an issue not only when eating raw citrus fruits but when eating fruit-based products such as jams and marmalades.

2. Ragweed and melons, bananas, cantaloupe

Weeds are cross-reactive with a number of foods, and the association between ragweed and these sweet fruits is among the most common. Ragweed season typically occurs between late summer through fall, but ragweed allergy sufferers may find themselves facing similar symptoms after biting into a banana or slice of melon or cantaloupe.

3. Grass and watermelon, melons, tomatoes and oranges

Grasses like Timothy and Johnson can wreak havoc on allergy sufferers. So, too, can their cross-reactive cousins in the produce aisle of your local supermarket.

4. Birch and peanuts, hazelnuts

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Many people suffer from common peanut allergies, while some may actually be allergic to birch tree pollen, which shares a similar protein to both peanuts and hazelnuts. According to PeanutAllergy.com, cooked and roasted nuts may also pose a threat, since their proteins are less sensitive to heat than others.

5. Mugwort and spices (anis, basil, chamomile, cilantro, dill, fennel, oregano, paprika, parsley, pepper, tarragon, thyme, and more)

Looking to spice up your life? It’s advised that you make sure you’re not allergic to mugwort, a weed that is cross-reactive with a number of spices you’ll find in your cupboard.

There are many other cross-reactive associations not listed here, which is why it’s important to understand both what your allergic sensitivities are, and what fruits, vegetables, nuts or spices they may be associated with.

Allergy awareness and avoidance are two positive steps you can take to combat allergies in your day-to-day life, but a better understanding of cross-reactivity is also important, helping ensure you know what to pick up – and what not to pick up – the next time you go grocery shopping.