Allergic Shock

Basic Information


Anaphylactic shock is an acute, life-threatening emergency. It is a fulminant, systemic reaction of the immune system to a foreign substance (an allergen). The exposure to the allergen can occur intra-venously (from prescribed or "street" drugs), from an injection (vaccines, antibiotics especially penicillin), from insect stings or bites, ingestion of foods (shellfish, peanut products), and, the least common route, through inhalation. Other less common causes are exercise-induced anaphylaxis, exposure to sulfites, and progesterone-induced anaphylaxis. The most life-threatening manifestations of anaphylaxis are total obstruction of the airway from tissue swelling and circulatory collapse (shock).

Anaphylaxis signs and symptoms

Any of the following may occur within seconds or a few minutes after exposure to a substance to which you are very allergic:

  • Tingling or numbness around the mouth.
  • Sneezing.
  • Coughing or wheezing.
  • Swelling around face or hands.
  • Feeling of anxiety.
  • Weak, rapid pulse.
  • Stomach cramps, vomiting, and diarrhea.
  • Itching all over, often accompanied by hives.
  • Watery eyes.
  • Tightness in the chest; difficult breathing.
  • Swelling or itching in the mouth or throat.
  • Pounding heart.
  • Faintness.
  • Loss of consciousness.

Not all symptoms occur. Seek immediate help for any.


Eating or receiving injections of something to which you are sensitive. The allergic response to neutralize or get rid of the material results in a life-threatening overreaction. Things that cause reactions most often include:

  • Medication of all types, especially penicillin.
  • Injections are much riskier than oral or eye drop medications.
  • Stings or bites from insects, such as bees, wasps, hornets, biting ants and some spiders.
  • Vaccines.
  • Pollen.
  • Injected chemicals used in some types of X-ray studies.
  • Foods, especially eggs, beans, seafood and fruit.
  • Exercise.

How is Anaphylaxis diagnosed?

  • History: If individuals are alert and coherent, they may be able to relate a history of previous episodes of anaphylaxis. The specific history is not important at this time. Initially, the individual complains of rash, itching, swelling, difficulty breathing, and chest tightness. Other manifestations are nausea, vomiting, diarrhea, and abdominal cramping. Anaphylaxis is easily diagnosed by its classic symptoms and signs.
  • Physical exam: The cutaneous signs are flushing, itchy, red, circumscribed, raised wheals (urticaria or "hives"), swelling (angioedema) affecting the face, eyes, lips, tongue, throat, or extremities, and profuse sweating (diaphoresis). Some respiratory symptoms are wheezing, shortness of breath (dyspnea), and a tight throat. Cardiovascular signs include a slow or fast pulse (bradycardia or tachycardia), low blood pressure (hypotension), fainting (syncope), disturbances of the heart rhythm (arrhythmias), and shock. Central nervous system disturbances can include delirium and seizures from hypoxia (oxygen deprivation).
  • Tests: No immediate tests are required to establish the diagnosis. Skin tests are done later to identify the allergen.

Risk increases with

  • A previous mild allergic response to things listed above.
  • Medical history of eczema, hay fever or asthma.

Preventive measures

If you have an allergic history:

  • Tell the doctor or dentist before accepting any medication. Before you are given a shot, ask what it is.
  • Keep an anaphylaxis kit, such as Ana-Kit, with you at all times. Be sure your family knows how to use the kit if you have a reaction.
  • If allergic to insect stings, wear protective clothing when outside.
  • Wear a medical alert type bracelet or pendant warning that you are allergic.
  • Always remain in the doctor's office 15 minutes after receiving any injection. Report any symptoms immediately.
  • Consider desensitization shots.

What might complicate it?

Complications include hypotension, arrhythmias, seizures, and an obstructed airway. Medical disorders of the respiratory or cardiovascular systems can worsen due to the anaphylactic reaction.

Expected outcomes

Anaphylactic reactions can be fatal if not treated quickly. Prompt treatment favors complete recovery.

Possible complications

Complications include hypotension, arrhythmias, seizures, and an obstructed airway. Medical disorders of the respiratory or cardiovascular systems can worsen due to the anaphylactic reaction.

Anaphylaxis treatment

Treatment consists of immediate administration of epinephrine and antihistamines, fluids through an intravenous line, maintenance of the airway by intubation if necessary, bronchodilators, and oxygen. Corticosteroids are started, but they require six to eight hours to take effect.

Individuals with a history of anaphylactic shock or severe allergic reactions must have access to an emergency kit. It contains a pre-loaded dose of epinephrine for self-administration in case of subsequent exposure to the allergen, often called "bee sting kits" in respect to one of the most frequent causes of anaphylaxis.

General measures

  • If you observe signs of anaphylaxis in someone and he or she stops breathing:
    Call or have someone call 911 (emergency) or call 0 (operator) for an ambulance or medical help. (If the victim is a child, perform lifesaving measures for 1 minute before calling for emergency help.)
    Begin mouth-to-mouth breathing immediately. If there is no heartbeat, give external cardiac massage.
    Don't stop CPR (cardiopulmonary resuscitation) until help arrives.
  • Be alert to the possibility of a reaction when taking any medicine, and be prepared to respond quickly if symptoms occur. If you have had a previous severe allergic reaction, always carry your anaphylaxis kit.
  • Long-term treatment involves desensitization therapy.


  • Epinephrine by injection is the only effective immediate treatment.
  • Aminophylline, cortisone drugs or antihistamines, given after the epinephrine, help prevent the return of acute symptoms.
Information Brand Generic Label Rating
Deltasone Prednisone
Pepcid Famotidine
Zantac Ranitidine
Phenergan Promethazine
Zyrtec Cetirizine
Atarax Hydroxyzine
Decadron Dexamethasone
Medrol Methylprednisolone


Avoid foods to which you are allergic.


Resume your normal activities as soon as symptoms improve after an attack. Stay under someone's observation for 24 hours in case symptoms recur.


Other possibilities include vasovagal syncope, pheochromocytoma, carcinoid syndrome, systemic mastocytosis, myocardial infarction, pulmonary embolism, asthma attack, hereditary angioedema, seizure disorder, or a transfusion reaction.

Appropriate specialists

Emergency and internal medicine specialist and allergist.

Notify your physician if

  • You or a family member has symptoms of anaphylaxis. This is an emergency! Get emergency help immediately.
  • New, unexplained symptoms develop. Drugs used in treatment may produce side effects.

Last updated 28 May 2015


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