Anaphylactic shock is a life-threatening allergic reaction that can be triggered by medications, foods, insect stings, latex, or exercise. It occurs when a sensitized individual is re-exposed to an allergen, activating antibodies that cause symptoms affecting the skin, gastrointestinal tract, respiratory system, and circulation. Common signs include itching, hives, swelling, nausea, vomiting, difficulty breathing, low blood pressure, and shock. Emergency treatment involves administering epinephrine, antihistamines, oxygen, and performing CPR if needed to prevent respiratory failure or circulatory collapse.