If you have a peanut allergy, your immune system has identified peanut protein as a threat to the body. This means that when you come into contact with peanuts, your immune system produces an antibody that clings to white blood cells. Those antibodies then release certain chemicals, such as histamine, that cause inflammation of tissue and lead to allergy symptoms. In most allergic reactions to peanuts, these symptoms may include an itchy throat, hives, indigestion, difficulty breathing, and runny nose. In severe, sometimes life-threatening cases, peanut allergy can trigger an anaphylactic reaction where heart rate speeds up, blood pressure falls, and the airway constricts.