Structural characterization of peanut allergen Ara h 5. Peanut allergen Ara h 5 is a member of the profilin family. This family of proteins includes a great number of pollen allergens food allergens and are considered pan-allergens an a big contributing factor of patients’ cross-reactivity to different foods and pollen. Structural characterization of profilin allergens is needed for understanding the allergenicity of food allergens and their cross-reactivities. ARS Researchers at Albany, California, and their collaborators solved the structure of peanut allergen Ara h 5 at a very high resolution (0.11 nanometers). The new result indicated that experimental structural information is required to avoid over-interpretation of homology-model-based prediction of immunoglobulin E epitopes. The structure of Ara h 5 and other profilin type of food allergens will facilitate the understanding of the allergenicity of food allergens and their cross-reactivity.