Anaphylactic Reaction

ExitCare ImageAn anaphylactic reaction is a sudden, severe allergic reaction that involves the whole body. It can be life threatening. A hospital stay is often required. People with asthma, eczema, or hay fever are slightly more likely to have an anaphylactic reaction.


An anaphylactic reaction may be caused by anything to which you are allergic. After being exposed to the allergic substance, your immune system becomes sensitized to it. When you are exposed to that allergic substance again, an allergic reaction can occur. Common causes of an anaphylactic reaction include:

  • Medicines.

  • Foods, especially peanuts, wheat, shellfish, milk, and eggs.

  • Insect bites or stings.

  • Blood products.

  • Chemicals, such as dyes, latex, and contrast material used for imaging tests.


When an allergic reaction occurs, the body releases histamine and other substances. These substances cause symptoms such as tightening of the airway. Symptoms often develop within seconds or minutes of exposure. Symptoms may include:

  • Skin rash or hives.

  • Itching.

  • Chest tightness.

  • Swelling of the eyes, tongue, or lips.

  • Trouble breathing or swallowing.

  • Lightheadedness or fainting.

  • Anxiety or confusion.

  • Stomach pains, vomiting, or diarrhea.

  • Nasal congestion.

  • A fast or irregular heartbeat (palpitations).


Diagnosis is based on your history of recent exposure to allergic substances, your symptoms, and a physical exam. Your caregiver may also perform blood or urine tests to confirm the diagnosis.


Epinephrine medicine is the main treatment for an anaphylactic reaction. Other medicines that may be used for treatment include antihistamines, steroids, and albuterol. In severe cases, fluids and medicine to support blood pressure may be given through an intravenous line (IV). Even if you improve after treatment, you need to be observed to make sure your condition does not get worse. This may require a stay in the hospital.


  • Wear a medical alert bracelet or necklace stating your allergy.

  • You and your family must learn how to use an anaphylaxis kit or give an epinephrine injection to temporarily treat an emergency allergic reaction. Always carry your epinephrine injection or anaphylaxis kit with you. This can be lifesaving if you have a severe reaction.

  • Do not drive or perform tasks after treatment until the medicines used to treat your reaction have worn off, or until your caregiver says it is okay.

  • If you have hives or a rash:

  • Take medicines as directed by your caregiver.

  • You may use an over-the-counter antihistamine (diphenhydramine) as needed.

  • Apply cold compresses to the skin or take baths in cool water. Avoid hot baths or showers.


  • You develop symptoms of an allergic reaction to a new substance. Symptoms may start right away or minutes later.

  • You develop a rash, hives, or itching.

  • You develop new symptoms.


  • You have swelling of the mouth, difficulty breathing, or wheezing.

  • You have a tight feeling in your chest or throat.

  • You develop hives, swelling, or itching all over your body.

  • You develop severe vomiting or diarrhea.

  • You feel faint or pass out.

This is an emergency. Use your epinephrine injection or anaphylaxis kit as you have been instructed. Call your local emergency services (911 in U.S.). Even if you improve after the injection, you need to be examined at a hospital emergency department.


  • Understand these instructions.

  • Will watch your condition.

  • Will get help right away if you are not doing well or get worse.