Peanut and/or tree nut allergy is a major health concern affecting over 1% of Americans. Although food allergy in general is the most common cause of anaphylaxis treated in emergency departments, reactions to nuts account for a disproportionate amount of deaths from food allergy. Peanut allergy is a Type I hypersensitivity (IgE mediated) immune response. Eight peanut allergens have been identified that are termed as Ara h 1 through Ara h 8. The diagnosis of peanut allergy can often be made or eliminated with a focused history and specific diagnostic testing. There is no effective method to cure peanut allergy. Therefore, the management of patients with peanut allergy focuses on 1) preventing inadvertent ingestions of peanut, 2) recognizing early signs of allergic reactions, and 3) properly treating peanut-induced symptoms should they occur. Epinephrine is clearly indicated for patients experiencing respiratory, cardiovascular, or neurologic compromise. Because inadvertent ingestion of peanut often leads to life threatening reactions and peanut allergy is often long-lived, many investigators are focusing on decreasing clinical reactivity after peanut allergy is established.