Anaphylaxis is a serious allergic reaction that affects multiple organ systems rapidly and can potentially cause death. It is caused by allergic reactions to foods, drugs, insect stings, latex, or other allergens. Symptoms can include any combination of skin issues like hives or swelling, respiratory symptoms like wheezing, gastrointestinal symptoms like vomiting, and cardiovascular symptoms like dizziness. Treatment involves using an epinephrine auto-injector like an EpiPen and calling emergency services, as the reaction can worsen quickly.