Anaphylaxis Causes and Symptoms

Anaphylaxis Causes and Symptoms

Anaphylaxis results from the release of histamine from mast cells in response to the presence of an allergen. Histamine causes the blood vessels

to dilate (expand), which lowers blood pressure. It also causes fluid to leak from the bloodstream into the tissues, which in turn causes the itchy skin swellings known as hives, and also lowers blood volume. These effects can lead to shock. Fluid can also leak into the air sacs in the lungs and make it difficult to breathe. Angioedema, or hivelike swelling of the tissues around the eyes or in the throat and mouth, can be severe enough to block the patient’s airway.

Anaphylaxis is considered a whole-body allergic reaction because so many different body systems can be affected:

• Skin: hives, angioedema, redness, itching, rash

• Digestive tract: nausea, abdominal pain or cramping, vomiting, diarrhea, itchy mouth or throat

• Circulation: pale or bluish skin color, weak or rapid pulse, feeling dizzy or lightheaded, low blood pressure, loss of consciousness, shock

• Breathing: wheezing, shortness of breath, throat tightness, cough, difficulty talking, chest pain or tightness, nasal congestion, trouble swallowing

• Psychological: panic, feelings of doom, intense anxiety