Anaphylaxis is a rare but life-threatening allergic reaction that affects many parts of the body at once. Like other allergic reactions, anaphylaxis is the body's overreaction to a foreign substance that ordinarily is harmless. Symptoms of anaphylaxis include flushing, hives, swelling of lips or tongue, difficulty breathing, nausea and vomiting, a decrease in blood pressure and ultimately, loss of consciousness.
These symptoms can occur within minutes of exposure to the offending allergen but also can develop after 30 minutes or more. In some cases, a delayed reaction may occur eight to 12 hours after the initial reaction. If symptoms develop quickly, the condition is more likely to be severe and potentially fatal.
Food is the most common trigger for anaphylaxis. Severe allergic reactions to foods such as peanuts, tree nuts (walnuts, pecans, almonds and cashews), fish, shellfish, cow's milk and eggs account for about half of all anaphylaxis cases and 100 U.S. deaths each year.
Stings from insects such as bees, wasps, hornets, yellow jackets and fire ants are the cause of about 500,000 allergy-related emergency room visits each year and at least 40 U.S. deaths from anaphylaxis.
Medications also can cause anaphylaxis, especially penicillin. Other commonly used medications that can trigger anaphylaxis include aspirin, anesthetics, antibiotics and pain relievers like ibuprofen.
Latex can trigger an allergic reaction. Latex is commonly found in medical products such as disposable gloves, syringes, stethoscopes and adhesive tapes.
Sometimes, doctors cannot pinpoint the cause of anaphylaxis. When a specific trigger cannot be found, it is said to be idiopathic anaphylaxis, meaning anaphylaxis without known cause.