Q. Are pine nuts a nut or seed, and should an adult with a severe nut allergy avoid them?
A. John Leung, MD, an allergist, co-director of the Food Allergy Center at the Floating Hospital for Children at Tufts Medical Center and a clinical professor at Tufts' Friedman School, responds, "Pine nuts are edible seeds of certain species of pine trees and are used in a variety of foods including Italian pesto sauce and pignoli cookies. Pine nuts (gymnosperms) are evolutionarily separated from flowering plants (angiosperms) to which all other nuts belong (peanut and tree nuts such as, walnut, hazelnut, cashew and pistachio).
"There is a very little information on potential cross-reactivity between pine nuts and other nuts. (Cross-reactivity happens when the immune system sees similar protein structures in different allergens.) One study showed cross-reactivity of pine nuts with peanuts, and another showed cross-reactivity of pine nuts with almonds. There are reports of people who had anaphylaxis to pine nuts who are also allergic to other nuts, and there are people who are only allergic to pine nuts but not to tree nuts or peanuts. A recent review in the Journal of Investigational Allergology and Clinical Immunology indicates that the great majority of pine-nut-allergic people do not have nut allergy.
"This issue, therefore, of whether pine nuts should be avoided in people who are allergic to other nuts can only be decided by clinical judgement. If tree nut or peanut allergy is severe, and people are motivated to try pine nuts, those individuals can be evaluated by a board-certified allergist using skin prick testing and potentially a supervised oral challenge in the doctor’s office."