Anaphylaxis
Anaphylaxis is a medical emergency which involves an acute, systemic allergic reaction that affects the entire body. It occurs after exposure to an allergen to which a person was previously sensitized.
Anaphylaxis is caused by an immunological mechanism, which involves an allergen reacting with certain antibodies called IgE. These antibodies attach to certain cells called mast cells or basophils which react with allergens. This interaction causes the release of chemicals called mediators. These mediators activate other parts of the immune system to produce an allergic reaction known as anaphylaxis. The best known mediator is histamine.
There are other reactions known as anaphylactoid which are trigged by non-IgE mechanisms and directly cause the release of mediators. These reactions may be caused by certain medications such as aspirin or ibuprofen, as well as IV contrast dyes.
According to one study, reported deaths due to anaphylaxis (from any one cause) occur at a rate of 0.4 cases out of one million people each year. The risk to any given person is approximately 1 percent. Systemic reactions to stings from bees, wasps, hornets, yellow jackets or fire ants can occur in 0.4 to 4 percent of the general population.
What are some signs and symptoms of Anaphylaxis?
The signs and symptoms of anaphylaxis may include, but are not limited to, anxiety itching of the skin, headache, nausea and vomiting, sneezing, coughing, abdominal cramps, hives, swelling of tissues such as lips or joints, diarrhea, shortness of breath, wheezing, low blood pressure, convulsions, and loss of consciousness. Furthermore, the eyes may itch, water and swell. Additional symptoms include itching of the mouth and/or throat, hoarseness, change of voice, nasal congestion, chest pain and tightness, a flush feeling of warmth, redness of the skin, cramping of the uterus and the sensation of needing to urinate.
Anaphylaxis has been mistaken for other reactions such as hyperventilation, anxiety attacks, alcohol intoxication, and low blood sugar. Skin testing or RAST blood testing may document your sensitivity to certain allergens such as bee venom, latex, foods and certain drugs that may cause anaphylaxis. On occasion, patients may experience anaphylactic-like symptoms (low blood pressure, convulsions) which are caused by other medical conditions such as heart attacks or epilepsy. In certain situations, a blood sample may be obtained at the time of the clinical event to test for the presence of serum Tryptase, which may indicated the symptoms are caused by an allergic mechanism (i.e. anaphylaxis).
What causes Anaphylaxis?
There are many agents that can cause anaphylaxis or anaphylactoid reactions. Drugs are the leading cause of anaphylaxis, with the major ones being antibiotics, seizure medications, muscle relaxants, and certain post-surgery fluids. Blood and blood products have also been implicated in these reactions.
Food and food additives are commonly blamed as a cause of anaphylaxis. The major foods implicated are milk, eggs, shellfish, tree nuts, and peanuts. Other foods that can cause reactions are legumes, whitefish, and celery. Certain foods have a high concentration of histamine, such as fish that has been improperly refrigerated. When ingested, histamine is absorbed and may cause an anaphylactoid type of reaction.
What is Exercise-Induced Anaphylaxis?
Exercise-induced anaphylaxis (EIA) is characterized by generalized itching with (or without) hives, decreased blood pressure, and narrowing of the upper respiratory tract. It is usually associated with increased climatic temperatures and intense exercise.
People who suffer from EIA need not have pre-existing asthma or allergies, nor does it occur after every incident of exercise. In some cases, EIA only occurs after ingestion of certain foods such as celery, chicken, shellfish, nuts, wheat and peaches. Persons with this condition should always have a partner who is able to administer injectible epinephrine. You must stop exercising at the first sign of anaphylaxis.
How do you treat Anaphylaxis?
Anaphylaxis is a medical emergency that must be treated immediately. Therapy includes epinephrine (adrenaline) and other medications such as antihistamines and steroids. The sooner the reaction is treated, the less severe it will be.
How do you prevent Anaphylaxis?
The best therapy for anaphylaxis is avoidance of the allergen. Individuals who are allergic to certain foods should always avoid them. Always follow your doctor's orders on prescribed medications. It is important to wait at least 20 minutes in the doctor's office following an injection of drugs or an allergy shot so that if a reactions occurs, it can be promptly treated. Give an accurate,
thorough medical history to your doctor. Those patients with known life-threatening allergies should carry a Medic-alert bracelet and should know how to use
injectible epinephrine.