Just eight foods account for most allergic reactions.

Although not all allergies are life-long, people who have allergic reactions to peanuts and tree nuts are often considered to have them throughout life.

The mechanisms underlying food allergies are not completely understood. But researchers at the Agricultural Research Service’s Food Processing and Sensory Quality Research Unit in New Orleans, La., are studying allergen immune system interactions involved in nut allergies.

People affected by nut allergy experience wide variation in the breadth and intensity of their allergic reactions. For example, among people who are allergic to a specific tree nut, one individual may be five times more allergic than another.

 (You might also be interested in Getting the truth out about peanut allergies).

Tree nuts can be members of several plant families. Though thought of as nuts, peanuts are not nuts. They are members of the Leguminosae family. Still, both nuts and legumes have commonalities: They both consist of a dry fruit contained inside a shell. Some, but not all, people who have allergies to certain tree nuts can still eat peanuts, and vice versa.


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In New Orleans, ARS chemist Soheila Maleki has worked with university collaborators on key components of a Structural Database of Allergenic Proteins (SDAP). The computational database was developed by Catherine Schein and colleagues at the University of Texas Medical Branch, in Galveston, Texas.

The team is in the process of validating SDAP’s ability to help predict when an individual will react to two or more different types of nuts. This condition is called “cross-reactivity.”

Foods, including peanuts and tree nuts, contain proteins, which are digested into smaller fragments called “peptides.” A peptide is called an “epitope” when it is recognized by antibodies — immune system components in the bloodstream. Immunoglobulin E (IgE) is an antibody that is elevated in allergic individuals. When IgE binds to the epitopes, the food is recognized as foreign by the immune system, and an allergic reaction occurs.

The proteins between cross-reactive nuts are thought to have similar IgE antibody-recognition sites. The researchers took known IgE binding sites (epitope sequences) from peanut and nut proteins and ran those through the SDAP database in order to predict cross-reactive epitopes in other nuts.