health

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