INTRODUCTION
Botanically, a tree nut is a dry hard fruit that grows in trees and does
not open to release its seed, such as chestnut, hazelnut, and acorn. In
everyday language, the term is used to describe a variety of edible
seeds of drupe fruits like walnuts, almonds, and
pistachios1. The most commonly consumed tree nuts in
Europe include almonds, hazelnuts, walnuts, pecan nuts, cashews,
pistachio nuts, Brazil nuts, and macadamia nuts2.
Peanut, although a legume, is often referred to together with tree nuts
due to their similar culinary use.
Tree nuts belong to the group of the eight major allergenic foods and,
along with peanuts, have been implicated in severe fatal or near-fatal
allergic reactions3. However, allergic manifestations
to nuts vary substantially, depending on several factors, such as the
implicated nut4, the sensitization to distinct
allergen components and the presence of co-factors5,6,
and even the process of the nuts before consumption7.
Almond, for example, rarely causes significant clinical
allergy8. Furthermore, allergy to different allergen
components influences the predicted severity of a reaction, ranging from
benign oropharyngeal symptoms to life-threatening
anaphylaxis9,10. Unlike peanut allergy, allergy to
tree nuts has been under-investigated. Evidence on the prevalence,
clinical manifestation, and natural history of tree nut allergy is
generally sparse, as has been recently reviewed5,6,11.
Recent studies12,13 suggest that allergy to tree nuts
is more common than peanut, in many countries, and poses a substantial
burden to patients and families. As with other food allergens, the
management relies on strict avoidance of the culprit nut (and often of
potentially cross-reacting foods) and symptomatic treatment of
accidental consumption. Food oral immunotherapy (OIT) is actively
investigated for the management of milk, egg, wheat, and peanut
allergy14. FDA (U.S. Food and Drug Administration),
EMA (European Medicines Agency), and NICE (U.K. National Institute for
Health and Care Excellence) have recently approved peanut OIT for
clinical practice. On the contrary, there is a lack of data on
desensitization approaches in managing tree nut allergy. This systematic
review aims to evaluate potential therapeutic options for the
desensitization of patients with IgE-mediated tree nut allergy.
The primary question was, “Which are the therapeutic options for the
desensitization of patients with IgE-mediated walnut or cashew or
pistachio or hazelnut, or almond allergy? What is the effectiveness and
safety of these options?”.