In some cases, individuals who are allergic to shellfish may also be allergic to okra due to the presence of similar proteins in both foods. This phenomenon is known as cross-reactivity. Cross-reactivity occurs when the immune system recognizes similar proteins in different foods as the same and produces an allergic reaction.

The proteins found in both shellfish and okra that can cause allergic reactions are called tropomyosins. Tropomyosins are structural proteins that are found in the muscle tissues of animals, including shellfish, as well as in plants, such as okra.