Tree nuts are a powerful and common source of food allergens that induce IgE-mediated allergic reactions. Health authorities endorse the intake of tree nuts because they are regarded as nutritious. Allergic reactions to nuts can lead to severe and occasionally lethal reactions. Allergies to tree nuts are observed worldwide and are found in up to 4.9% of people in unspecific populations. Over the last 2 decades, the rates of allergic reactions and anaphylaxis have increased in different countries. Most proteins implicated in tree nut allergic reactions are members of the lipid transfer protein, 2S albumin, vicilin, legumin, and oleosin protein families. Bet v 1 homologs and profilins are involved in pollen-related tree nut allergies. Systematic literature reviews and meta-analyses on the diagnostic accuracy of specific immunoglobulin E (sIgE) for commercially available nut components have recently been published. IgE testing of the storage proteins Cor a 14, Cor a 9, Jug r 1, and Ana o 3 increases diagnostic specificity in assessing hazelnut, walnut, and cashew allergies in children, respectively. The resolution of tree nut allergies has been reported; however, only a few studies are available in this regard. Complete avoidance of nuts is the safest approach for nut-allergic subjects. However, this is difficult to achieve and can result in a severely restricted diet. Patients can eat nuts that they know are safe at home, but should avoid them when eating out because of the risk of cross-contamination. Nuts have become part of a modern healthy diet, and this enhanced consumption is reflected in an increased prevalence of nut allergies.