Cross-reactivity occurs when your body's immune system identifies the proteins in one substance (e.g. pollen) and the proteins in another (e.g. fruit & vegetables) as being similar. When you come into contact with either, whether it’s a protein in something that you are truly allergic to or not, your immune system can react in the same way, which can then cause your allergic symptoms.

All that matters to the immune system, is that the proteins are structurally similar or biologically related and cross-reactivity can occur. The risk of cross-reactivity needs to be assessed by a healthcare professional, and important foods should never be removed from a diet without a confirmed diagnosis.