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(Anaphylactic Reaction)

Pronounced: ANNA-fill-AX-is

En Español (Spanish Version)


Anaphylaxis is a severe, sometimes life-threatening, allergic reaction. The reaction includes hives, facial swelling, low blood pressure, and breathing difficulties.


Substances that cause anaphylaxis are often called allergens or triggers. Common triggers include:

  • Medications, including antibiotics, seizure medications, and muscle relaxants
  • Insect stings or bites
  • Vaccines
  • Injected dyes used in some types of x-rays
  • Foods and food additives, especially eggs, peanuts, seafood, cow's milk, soy, and sulfites
  • Blood products
  • Latex products (gloves, medical tubing, dental dams, condoms)

Allergic Reaction to Medication (Hives)

Hives Medication

© 2008 Nucleus Medical Art, Inc.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors include:

  • Previous mild allergic reaction to the substances listed above
  • History of eczema , hay fever , or asthma
  • Children who have spina bifida and urogenital defects (due to the heavy exposure to latex they experience during multiple surgeries)


The symptoms of anaphylaxis usually occur within minutes after exposure to an allergen, but can occur hours later. Symptoms may be mild or very severe, including death. They include:

  • Hives and itching
  • Swelling, redness, stinging or burning, especially on the face, mouth, eyes, or hands
  • Lightheadedness, caused by a drop in blood pressure
  • Obstruction of the nose, mouth, and throat
  • Severe respiratory distress
  • Chest tightness, shortness of breath, wheezing
  • Nausea, vomiting, cramping, diarrhea
  • Heart arrhythmias
  • Convulsions
  • Shock ( occurs in 30% of cases)


Diagnosis of anaphylaxis is based on the symptoms. The doctor will suspect anaphylaxis if you have symptoms and have been exposed to a likely allergen.


Anaphylaxis is a medical emergency that requires immediate medical treatment, including:

  • Epinephrine (Adrenaline) injection—makes blood vessels contract, relaxes the airway, stops itching and hives, and relieves gastrointestinal. cramping
  • Other medications—corticosteroids and/or antihistamines may be given after the epinephrine to decrease inflammation and improve breathing.
  • Bronchodilators—to improve breathing
  • Intravenous fluids
  • Oxygen
  • Cardiopulmonary resuscitation (CPR)—may be necessary in severe cases when anaphylaxis lead to cardiovascular collapse. Severe anaphylaxis may require mechanical ventilation until swelling is brought under control.


Avoiding substances that trigger anaphylaxis is the best prevention. In addition:

  • Allergy shots can decrease the risk of anaphylaxis and reduce the severity of the reactions.
  • Wear a Medic-Alert bracelet that lists your allergies.
  • Tell your doctor or dentist about your allergies before taking any medication. When possible, ask that medications be taken as a pill. Allergic reactions can be more severe with injected medications.
  • Keep an anaphylaxis kit (Ana-Kit®, Epi-Pen®) with you at home, work, in the car, and when you travel. Be sure family and friends know how to use the kit too.
  • Make sure the school nurse knows about any allergies your child has.
  • If allergic to insect stings, wear protective clothing when outside.
  • Always remain in the doctor's or dentist's office 15 minutes after receiving an injection. Report any symptoms immediately.


American Academy of Allergy, Asthma, and Immunology

The Food Allergy and Anaphylaxis Network


Allergy Asthma Information Association

Calgary Allergy Network


Anaphylaxis. Emedicine . 2001 May 2.

Kay AB. Allergy and allergic diseases–second of two parts. N Engl J Med . 2001;344:109-113.

National Institute of Allergy and Infectious Diseases website. Available at: . Accessed March 25, 2007.

Pumphrey, R. Anaphylaxis: can we tell who is at risk of a fatal reaction?. Curr Opin Allergy Clin Immunol 2004; 4:285.

Sampson, HA, Munoz-Furlong, A, Campbell, RL, et al. Second symposium on the definition and management of anaphylaxis: summary report--Second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium. J Allergy Clin Immunol 2006; 117:391.

Winbery, SL, Lieberman, PL. Anaphylaxis. Immunol Allergy Clin North Am 1995; 15:447.

Last reviewed March 2008 by Marcin Chwistek, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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