Anaphylaxis - Symptoms, Causes, and Treatment

Severe Allergic Reactions

Anaphylaxis is a severe allergic reaction that can affect many organs of the body, including the skin, lungs, gastrointestinal tract, as well as the eyes, nose and throat. ADAM

There is no single definition of anaphylaxis that is agreed upon by most experts in the field of allergy. In general, anaphylaxis is a life-threatening reaction caused by the release of chemicals, such as histamine, leukotrienes, and tryptase, from mast cells. This may result in a variety of symptoms, including low blood pressure (shock), trouble breathing, and skin symptoms such as hives and swelling.

There are a number of causes of anaphylaxis, many of which are allergic in nature and involve allergic antibodies (IgE). However, not all causes involve IgE; exceptions include IV dye reactions and aspirin (NSAID) allergy.

What are the Symptoms of Anaphylaxis?

The symptoms of anaphylaxis vary, and may not all be present in a single person experiencing anaphylaxis. I tend to consider anaphylaxis when I see a patient with skin symptoms as well as the involvement of at least one other organ system.

Symptoms may include:

  • Skin symptoms, such as urticaria and angioedema, pruritus (itching) or flushing
  • Respiratory symptoms, such as shortness of breath, wheezing and coughing
  • Circulatory symptoms, such as rapid heart rate, lightheadedness, and low blood pressure
  • Gastrointestinal symptoms, such as nausea, vomiting, diarrhea and abdominal cramps
  • Allergic rhinitis symptoms, such as sneezing, post-nasal drip and itchy nose and eyes
  • Other symptoms, such as menstrual cramps in women, metallic taste, sense of panic

What Causes Anaphylaxis?

There is a wide variety of causes of anaphylaxis, and therefore it is important for an allergist/immunologist to carefully review a person’s history in order to identify the cause of the reaction.

Causes of anaphylaxis include, but are not limited to:

It is extremely rare for a person to experience anaphylaxis as a result of airborne allergens, such as pollens, molds, pet danders or dust mite allergen. However, these allergens commonly trigger hay fever and hives.

How is Anaphylaxis Diagnosed?

The diagnosis of anaphylaxis is usually made when a person’s symptoms are consistent with the syndrome. After a person’s history of symptoms, along with the events that occurred shortly before the onset of the reaction are considered, an allergist/immunologist can narrow the likely causes.

Typically, skin testing can be performed for a variety of foods, medicines, venoms and latex in an attempt to identify the allergen. Various blood tests may also be performed to confirm anaphylaxis (such as checking a serum tryptase level), as well as other tests to ensure that a disease that mimics anaphylaxis is not the cause of the symptoms.

How is Anaphylaxis Treated?

The initial treatment of anaphylaxis includes the removal of the offending allergen (remove the bee stinger; stop taking the medication; remove the latex from the person’s body, etc.), as well as the use of various medications, such as injectable epinephrine, antihistamines, and corticosteroids. Epinephrine is the drug of choice for the initial treatment of anaphylaxis and is available in self-injectable kits (such as the Epi-Pen) for people who are prone to anaphylaxis to carry with them.

These people should also consider wearing a Medic-Alert bracelet so that medical personnel can quickly identify their condition in an emergency.

Antihistamines are the next most important medication used to treat the acute symptoms of anaphylaxis. Typically, these antihistamines can be given in oral forms; more severe cases of anaphylaxis may require injected or intravenous antihistamines, such as Benadryl (diphenhydramine).

The use of corticosteroids, in oral, injected or intravenous form, may be useful in the prevention of prolonged or recurrent symptoms of anaphylaxis. However, these medications are not likely to help the immediate symptoms of anaphylaxis.

The prevention of future anaphylaxis is often the job of an allergist, who can help a person identify the cause of the reaction, as well as how to avoid future exposures. In the case of venom allergy, immunotherapy can be given to cure the allergy.

In the case of IV contrast dye allergy, the use of preventative medications, including antihistamines and corticosteroids, can help to reduce or prevent anaphylaxis if future doses of IV dye are needed.

In rare circumstances, antihistamines and corticosteroids may need to be given on a daily basis in order to prevent symptoms of anaphylaxis.


Lieberman P, Kemp SF, Oppenheimer J, et al. The Diagnosis and Management of Anaphylaxis: An Updated Practice Parameter. J Allergy Clin Immunol. 2005; 115:S483-523.

Kemp SF, Lockey RF. Anaphylaxis: A Review of Causes and Mechanisms. J Allergy Clin Immunol. 2002; 110:341-8.

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