Anaphylaxis is a rare, severe allergic reaction that often begins immediately after an individual has been exposed to a particular allergen. Without prompt emergency treatment, anaphylaxis may interfere with a person’s ability to breathe, or lead to shock.

Anaphylaxis does not occur on an individual’s first exposure to an allergen. Instead, prior exposures sensitize the person to the antigen. Because these initial exposures occur without incident, the individual may be unaware they have taken place.

After sensitization, the next encounter with the allergen will trigger an allergic reaction. Anaphylaxis is a potentially dangerous allergic reaction affecting two or more body systems. Symptoms of anaphylaxis include hives, itching, swelling or redness of the skin, a drop in blood pressure, vomiting and/or breathing difficulties.

An anaphylactic reaction can quickly progress to life-threatening anaphylactic shock, which is characterized by difficulty breathing and a dangerous drop in blood pressure. Emergency treatment with the drug epinephrine (allergy kit) usually reverses symptoms quickly. Epinephrine should be taken at the first sign of anaphylaxis. Cardiopulmonary resuscitation (CPR) may be necessary. Preventative steps also can be taken to reduce the potential for an occurrence of this rare reaction.