Anaphylaxis

by Editorial Staff and Contributors

Definition

Anaphylaxis is a severe, sometimes life-threatening, allergic reaction.

Causes

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

Medications (eg, antibiotics, seizure medications, muscle relaxants)
Insect stings or bites
Vaccines
Foods and food additives, especially eggs, peanuts, seafood, cow's milk, soy, and tree nuts
Blood products
Latex products (eg, gloves, medical tubing, condoms)

Allergic Reaction to Medication (Hives)

Hives Medication © 2009 Nucleus Medical Art, Inc.

Some triggers, like dyes used in x-ray procedures, can cause a reaction similar to anaphylaxis.

Risk Factors

These factors increase your chance of developing anaphylaxis. Tell your doctor if you have any of these risk factors:

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

Symptoms

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
Low blood pressure, shock ( occurs in 30% of cases)

Diagnosis

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

Treatment

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

Epinephrine (adrenaline) injection—makes blood vessels constrict, 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 leads to cardiovascular collapse. Severe anaphylaxis may require mechanical ventilation until swelling is brought under control.

If you are diagnosed with anaphylaxis, follow your doctor's instructions.

Prevention

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 to certain triggers.
Wear a medical alert jewelry 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 self-injectable epinephrine (eg, Epi-Pen, Twin-ject) 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 30 minutes after receiving an injection. Report any symptoms right away.