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Anaphylaxis

What is anaphylaxis?

Anaphylaxis is the most severe form of an allergic reaction and can be life-threatening. Anaphylaxis, or anaphylactic shock, involves the entire body. A number of allergens and a number of circumstances can cause it. The reaction occurs when specific cells in the body’s immune system release chemicals that have an effect on the body.

When the reaction is caused by an allergen, it is called anaphylaxis. If the reaction is caused by a non-allergen, it is called an anaphylactoid reaction. The symptoms are the same and, in most cases, the treatment is the same. The two processes differ in how they cause the reaction and how they can be diagnosed. With anaphylactic reactions, the cause is an antibody (a protein that the immune system uses to identify foreign invaders) made by the patient. In this case, the antibody is an IgE (Immunoglobulin E).

Allergens are substances that cause the patient to have a specific allergic response—creation of an IgE antibody—to the substance. Skin testing can discover substances that cause the patient to make this antibody. There are situations when the reaction occurs by a different mechanism. The substance causes the reaction but does not involve IgE. In these situations, skin testing or blood testing for allergy will not help.

Examples of the two types of reactions:

  • Due to IgE (related to allergy)
    • Food
    • Stinging insects
    • Medications, especially antibiotics
    • Injections, like vaccines and allergy shots
  • Non-IgE (not related to allergy)
    • Infusion of human blood products
    • Non-steroidal anti-inflammatory agents (NSAIDS like aspirin and ibuprofen)
    • Direct mast cell releasers like contrast media or chemotherapeutic agents
    • Idiopathic, in which no cause is found

What happens with anaphylaxis?

An anaphylaxis reaction can involve a number of body systems. Usually there will be a skin reaction (such as hives or swelling) plus a second organ system involved in the reaction, like the gastrointestinal tract, cardiovascular system or airway.

What are the signs of anaphylaxis?

  • The skin may show flushing, hives, swelling or become itchy
  • Cardiovascular system signs include rapid heart rate, low blood pressure, shock, arrhythmias and loss of consciousness
  • Gastrointestinal system signs include distension (abnormal pressure and expansion of the abdomen), vomiting, diarrhea, nausea, pain or cramps
  • Respiratory system signs include swelling of the airway, wheezing and asphyxiation
  • Other symptoms may include sweating, a sense of impending doom and a metallic taste in the mouth

Facts On Anaphylaxis

Patients might experience an anaphylaxis reaction in as little as a few seconds after exposure to the allergen or the reaction may build over a few hours. The more serious reactions tend to occur quickly. Reactions may come in two phases—an early phase and one that may be delayed for 6-10 hours. When the reaction occurs more than two hours after exposure, it tends to be less severe. Over 70 percent of patients who have anaphylaxis will have respiratory system symptoms and over 80 percent will have hives or swelling of the deep tissue of the skin, lips or tongue.

Some people experience anaphylaxis after exercise. Patients with this syndrome experience generalized itchiness of the skin with or without hives, low blood pressure and difficulty breathing. Eating food such as celery, wheat or shellfish a few hours before exercising may contribute to the problem. The list of foods associated with this condition is growing.

How is anaphylaxis treated?

Anaphylaxis is a medical emergency. Epinephrine or adrenaline should be given immediately. An antihistamine should also be given. These reactions need to be treated as soon as possible and the patient should be taken to the nearest emergency facility. The sooner the reaction is treated, the less severe it will be. Remove any possible offending agents that may cause the reaction to get worse. Benadryl (diphenhydramine) is often given for anaphylactic reactions; however, it will not help treat the mediators involved in a life-threatening reaction and should not be depended upon as the only treatment for anaphylaxis. Benadryl will help treat the itch due to hives. A major concern is when a patient uses Benadryl instead of injectable epinephrine.

How can anaphylaxis be prevented?

The best treatment for anaphylaxis is avoidance. An evaluation will help identify the allergen and lead to information on how to avoid it. A specialist should be involved. You should know how to administer epinephrine to your child. Patients who experience anaphylaxis should wear a medical alert bracelet.

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