Question

Explain the events that occur during anaphylactic reactions, including descriptions and examples of both systemic anaphylaxis and localized anaphylaxis. Describe how anaphylaxis can sometimes be prevented by desensitization methods.

Answer 1

Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. It typically causes more than one of the following: an itchy rash, throat or tongue swelling, shortness of breath, vomiting, lightheadedness, and low blood pressure.These symptoms typically come on over minutes to hours.

Common causes include insect bites and stings, foods, and medications. Other causes include latex exposure and exercise.Additionally cases may occur without an obvious reason. The mechanism involves the release of mediators from certain types of white blood cells triggered by either immunologic or non-immunologic mechanisms.^[6] Diagnosis is based on the presenting symptoms and signs after exposure to a potential allergen.

The primary treatment of anaphylaxis is epinephrine injection into a muscle, intravenous fluids, and positioning the person flat. Additional doses of epinephrine may be required. Other measures, such as antihistamines and steroids, are complementary. Carrying an epinephrine autoinjector and identification regarding the condition is recommended in people with a history of anaphylaxis.

Systematic anaphylaxis-

A reaction between IgE antibodies bound to mast cells and an allergen that causes the sudden release of immunological mediators in the skin, respiratory, cardiovascular, and gastrointestinal systems. The consequences may range from mild, e.g., itching, hives, to life-threatening (airway obstruction and shock).

Localized anaphylaxis-

Localized anaphylaxis (atopic allergy) is a less severe form of anaphylaxis, whose symptoms depend primarily upon how the allergen enters the body. In hay fever (allergic rhinitis) the allergen enters the upper respiratory tract. Common allergens in hay fever include pet dander, pollen, fungal spores and household dust mites. Exposure to these particles causes the typical symptoms of hay fever, i.e., runny nose, itchy eyes, coughing and sneezing, most of which are indicative of the action of mast cells. Treatment typically involves the use of antihistamines to block the action of histamine released by mast cells.

Prevented by desensitization-

Avoidance of the trigger of anaphylaxis is recommended. In cases where this may not be possible, desensitization may be an option. Immunotherapy with Hymenoptera venoms is effective at desensitizing 80–90% of adults and 98% of children against allergies to bees, wasps, hornets, yellowjackets, and fire ants. Oral immunotherapy may be effective at desensitizing some people to certain food including milk, eggs, nuts and peanuts; however, adverse effects are common. For example, many people develop an itchy throat, cough, or lip swelling during immunotherapy. Desensitization is also possible for many medications, however it is advised that most people simply avoid the agent in question. In those who react to latex it may be important to avoid cross-reactive foods such as avocados, bananas, and potatoes among others.