Symptoms
Symptoms develop rapidly, often within seconds or minutes. They may include the following:
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Causes
Anaphylaxis is an severe, whole-body allergic reaction. After an initial exposure to a substance like bee sting toxin, the person's immune system becomes sensitized to that allergen. On a subsequent exposure, an allergic reaction occurs. This reaction is sudden, severe, and involves the whole body.
Tissues in different parts of the body release histamine and other substances. This causes constriction of the airways, resulting in wheezing , difficulty breathing , and gastrointestinal symptoms such as abdominal pain, cramps, vomiting, and diarrhea.
Histamine causes the blood vessels to dilate (which lowers blood pressure) and fluid to leak from the bloodstream into the tissues (which lowers the blood volume). These effects result in shock . Fluid can leak into the alveoli (air sacs) of the lungs, causing pulmonary edema .
Hives and angioedema (hives on the lips, eyelids, throat, and/or tongue) ...
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Treatment
Anaphylaxis is an emergency condition requiring immediate professional medical attention. Assessment of the ABC's (airway, breathing, and circulation from Basic Life Support) should be done in all suspected anaphylactic reactions.
CPR should be initiated if needed. People with known severe allergic reactions may carry an Epi-Pen or other allergy kit, and should be assisted if necessary. Emergency interventions by paramedics or physicians may include placing a tube through the nose or mouth into the airway ( endotracheal intubation ) or emergency surgery to place a tube directly into the trachea ( tracheostomy or cricothyrotomy).
Epinephrine should be given by injection without delay. This opens the airways and raises the blood pressure by constricting blood vessels.
Treatment for shock includes intravenous fluids and medications that support the actions of the heart and circulatory system.
Antihistamines, such as diphenhydramine; and corticosteroids, such as ...
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Other Names
Anaphylactic reaction; Anaphylactic shock; Shock - anaphylactic
Outlook (Prognosis)
Anaphylaxis is a severe disorder which has a poor prognosis without prompt treatment. Symptoms, however, usually resolve with appropriate therapy, underscoring the importance of action.
Prevention
Avoid known allergens. Any person experiencing an allergic reaction should be monitored, although monitoring may be done at home in mild cases.
Occasionally, people who have a history of drug allergies may safely be given the offending medication after pretreatment with corticosteroids (prednisone) and antihistamines (diphenhydramine).
People who have a history of allergy to insect bites/stings should be instructed to carry (and use) an emergency kit consisting of injectable epinephrine and chewable antihistamine. They should also wear a Medic-Alert or similar bracelet/necklace stating their allergy.
Exams and Tests
Examination of the skin may show hives and swelling of the eyes or face. The skin may be blue from lack of oxygen or may be pale from shock. Angioedema in the throat may be severe enough to block the airway.
Listening to the lungs with a stethoscope may reveal wheezing or indicate fluid (pulmonary edema). The pulse is rapid, and blood pressure may be low. Weakness, pale skin, heart arrhythmias, mental confusion, and other signs may indicate shock.
Testing for the specific allergen that caused anaphylaxis (if the cause is not obvious) is postponed until after treatment.
References
The diagnosis and management of anaphylaxis: an updated practice parameter. J Allergy Clin Immunol . 2005 Mar;115(3 Suppl):S483-523.