Anaphylaxis is a rapid onset allergic reaction that can be life-threatening and requires immediate diagnosis and treatment. It is caused by the release of vasoactive and bronchial mediators from mast cells and basophils after exposure to allergens such as drugs, foods, stings, vaccines, latex, or contrast material. Symptoms involve two or more organ systems and include skin issues like hives, respiratory issues like wheezing, hypotension, and gastrointestinal cramps or vomiting. Epinephrine is the first-line treatment as it reduces edema and constricts blood vessels while opening airways.