What is Cross-Reactivity?

You diligently keep your child away from all ingredients that could cause a reaction from their allergy, whether it’s to wheat, nuts, milk or another allergen. But are you aware of foods that could impact your child because of cross-reactivity? Your child may also react to foods that are similar or related to the allergens. Let’s talk about what this means and how you can use this information.

How Does Cross-Reactivity Work?

Your child may experience cross-reactivity from different foods than the allergen you know your child is allergic to. This comes down to the proteins in a food. When different foods have similar proteins, your child’s immune system may think they are the same. It could think the proteins in the goat milk you give your child is the same as the protein in the cow’s milk your child is allergic to and cause an allergic reaction in response.

Cross-reactivity is also known as a secondary food allergy. The likelihood this reaction will happen varies, and the prevalence of allergy cross-reactivity is not entirely known. Your child could only be allergic to a specific allergen without having cross-reactivity, while another child will experience cross-reactivity to a whole food group.

Also, the risk of cross-reactivity is higher for some allergens, such as milk, than for others, such as legumes. It’s also common for the reaction to go beyond food. For example, your child could show a cross-reactivity to certain foods when they have a pollen or latex allergy. This happens because these components have a similar protein to that found in certain produce. 

You may think your child has multiple allergies, but it’s possible for one reaction to be a cross-reaction to a primary allergy.

How to Handle Cross-Reactivity

Identify Secondary Allergens

If you know your child is allergic to one type of food, it’s worth considering cross-reactivity to foods in the same food group. You can rely on a food and symptom diary to figure out which foods may be triggering reactions. Secondary allergies generally create less severe reactions, although it’s possible for them to be severe. To confirm a cross-reactivity, your allergist can perform a skin or blood test, and possibly an oral test if needed.

Common Environmental Cross-Reactivity

Also, be aware of common cross-reactions to look out for. This knowledge can help you avoid or manage exposure to both the primary and secondary allergens.

If your child has an allergy to tree pollen, such as birch trees, they may have a cross-reaction to these foods:

  • Certain fruits, including peaches, plums, kiwi, apples, pears, cherries, lychee and nectarines

  • Nuts, including almonds and hazelnuts

  • Certain vegetables, including celery, carrots and raw potatoes

  • Soybeans

If your child has a ragweed allergy, they may cross-react to:

  • Banana

  • Melon

  • Cucumber

  • Tomato

If your child is allergic to latex, they may also react to:

  • Certain fruits such as fig, banana, kiwi, avocado, tomato and pineapple

  • Certain vegetables such as potato and celery

  • Chestnuts

  • Buckwheat flour

If your child has a mugwort allergy, they may cross-react to:

  • Certain fruits such  as mango, lychee and grapes

  • Certain vegetables such as celery and carrot

  • Sunflower seeds

  • Certain herbs and spices such as cumin, coriander, fennel seed, anise and parsley

There are also less common cross-reactions from environmental allergens. For example, a dust mite allergy could create a secondary reaction to certain seafood, while a grass allergy could cause a reaction to certain grains.

Tips for Handling Cross-Reactivity

Consider these tips or ask your allergist about them:

  • See if you only need to abstain from the food during pollen season.

  • Cook or peel fruits and vegetables to see if that takes away the reaction.

  • Try different varieties, such as a different type of apple.

  • Reduce stress to reduce the severity of a reaction.

  • Have an emergency medication in case a reaction becomes severe.