Anaphylaxis is an acute, potentially life-threatening reaction caused by the sudden release of mast cell mediators. It most often results from immunoglobulin E (IgE)-mediated reactions to foods, drugs, and insect stings. Anaphylaxis can be difficult to recognize because its presentation is variable. Epinephrine is the first-line treatment for anaphylaxis and should be administered immediately via intramuscular injection into the outer thigh. Long-term management involves patient education, confirmation of triggers through allergy testing, and prescribing epinephrine autoinjectors with instructions on how and when to use them.