A tree nut allergy is an immune system reaction to proteins found in tree nuts, which include nuts like walnuts, almonds, cashews, hazelnuts, and pistachios. Symptoms can range from mild, such as hives or stomach pain, to severe, including anaphylaxis, a life-threatening reaction that requires immediate medical attention. People with a tree nut allergy must avoid all tree nuts and products containing them. It's important to read food labels carefully, as tree nuts can be hidden in many processed foods. Consulting with a healthcare provider can help manage the allergy and provide guidance on safe eating practices.