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Anaphylaxis (cont.)

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Are there any disorders that appear similar to anaphylaxis?

Several disorders may appear similar to anaphylaxis. Fainting (vasovagal reaction) is the reaction that is most likely to be confused with anaphylaxis. The key differences are that in a fainting episode, the affected person typically has a slow pulse, cool and pale skin, and no hives or difficulty breathing. Other conditions, such as heart attacks, blood clots to the lungs (pulmonary embolus), septic shock, and panic attacks can also be confused with anaphylaxis.

How is anaphylaxis diagnosed?

Anaphylaxis is a clinical diagnosis and is usually diagnosed by the patterns of symptoms listed above. If someone thinks he or she is having an anaphylactic reaction, the first and most important step is to treat with self-injectable epinephrine and/or seek emergency care. Once the acute reaction has been treated with epinephrine, one must seek urgent medical care to monitor for the risk of a biphasic reaction. Referral to an allergist is also typically recommended. The allergist will assess whether or not the reaction was indeed allergic in nature. Sometimes, a careful and detailed medical history and selected blood or skin tests can identify the trigger. The medical history focuses on exposures such as foods, medications, and stings preceding the anaphylactic reaction. In rare cases, exercise or alcohol may be a factor in anaphylaxis.

Table 1: The Common Triggers of Anaphylaxis
Causes - IgE MediatedExamples
MedicationsAntibiotics (penicillin, cephalosporins), muscle paralytics used in anesthesia, NSAIDs, platinum-based chemotherapy, others
Insect stingsHornet, wasp, yellow jacket, honey bee, fire ant
FoodsPeanuts, tree nuts, fish, shellfish, eggs, milk, soy, wheat, sesame
VaccinesAllergy shots
HormonesInsulin, possibly progesterone
LatexRubber products
Causes - Non-IgE-MediatedExamples
MedicationNSAIDS, morphine, IV iron, gamma globulin, IV iron

Exercise-induced anaphylaxis: Exercise-induced anaphylaxis is a rare condition that presents with the same symptoms as anaphylaxis but is triggered by exercise. Exercise-induced anaphylaxis can be food-dependent in which symptoms occur with exercise only after consuming specific foods, such as celery, wheat, alcohol, or shellfish. Early symptoms are usually flushing and itching, which may progress to other typical symptoms of anaphylaxis if the exercise continues. Premedication with antihistamines or other drugs does not consistently prevent EIA. Warming up slowly, avoiding eating two to four hours before exercise, exercising with a partner, and carrying emergency epinephrine kits is mandatory for those at risk for exercise-induced anaphylaxis. If symptoms occur despite these measures, then exercise avoidance may be recommended.

When no cause can be found for anaphylaxis, it is termed idiopathic. Recent reports suggest that 25% of all episodes of anaphylaxis are idiopathic. For frequent episodes of anaphylaxis, a physician may recommend a combination of antihistamine, leukotriene inhibitors, or oral steroids to reduce the severity of attacks. There is also some evidence that a biologic medication, omalizumab (Xolair), which binds IgE, may help with idiopathic anaphylaxis.

Medically Reviewed by a Doctor on 7/21/2016


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