Anaphylaxis is a severe life-threatening allergic reaction. It can occur in seconds or minutes of exposure to an allergen.

Chemicals released by the immune system during anaphylaxis can cause anaphylactic shock. In anaphylactic shock the blood pressure drops suddenly, airways narrow and block normal breathing. Triggers of anaphylaxis include medications, insect venom, certain foods and latex.

Anaphylaxis requires immediate medical attention and an injection of epinephrine. If the condition is not treated immediately, it can lead to unconsciousness or death.



The symptoms of anaphylaxis occur within minutes of exposure to an allergen.

The symptoms of anaphylaxis include:

  • Skin reactions such as hives and itching and flushed or pale skin
  • Feeling of warmth
  • Sensation of a lump in the throat
  • Constriction of the airways and a swollen tongue or throat that can cause wheezing and trouble breathing
  • Weak and rapid pulse
  • Nausea, vomiting or diarrhea
  • Dizziness or fainting


Some people’s immune systems overreact to substances and cause allergic reactions. During an allergic reaction the immune system sets off a chemical chain reaction that results in allergy symptoms. A severe allergic reaction can lead to anaphylaxis.

Common triggers of anaphylaxis include:

  • Certain medications, especially penicillin
  • Foods such as peanuts, tree nuts, wheat, fish, shellfish, milk and eggs
  • Insect stings

Less common triggers include:

  • Latex
  • Medications used in anesthesia
  • Exercise

Symptoms of anaphylaxis can sometimes occur due to aspirin and other drugs as well as the intravenous contrast used in some X-ray imaging tests. However, allergy antibodies do not trigger this type of anaphylactic reaction.

In some cases, the cause of anaphylaxis cannot be identified. This is called idiopathic anaphylaxis.

Risk factors

Risk factors for anaphylaxis include:

  • Personal history of anaphylaxis
  • Allergies or asthma
  • Family history (refers mainly to exercise-induced anaphylaxis)


A severe anaphylactic reaction can be life threatening because it can stop the breathing or the heart. If this case, CPR and other emergency treatment is required.


The best way to prevent an anaphylactic reaction is to avoid substances that trigger the reaction.

Steps to prevent an anaphylactic attack include:

  • Wearing a medical alert necklace or bracelet
  • Alert doctors of any drug allergies
  • Keeping a properly stocked emergency kit
  • Being careful around insects if allergic to insect stings
  • Reading food labels if allergic to any foods