health

Anaphylaxis is a reaction that occurs in people who are severely allergic to
certain foods or other substances. People with individual or family histories
of hay fever, asthma, eczema, or food allergies are at increased risk
of having an anaphylactic reaction at some point in their lives. People
with asthma are particularly likely to have an anaphylactic reaction to
food at some point. Anaphylaxis is an overreaction to an allergen caused
by the body’s production of an antibody called immunoglobulin E or
IgE. When a person who is susceptible to allergies first comes into contact
with an allergen, the person’s immune system produces IgE antibodies
that are specific to that allergen. The IgE antibodies then attach
themselves to the surface of mast cells, which are specialized cells that lie
within the connective tissue near the blood vessels. The next time the
person encounters that specific allergen, the IgE antibodies trigger the
release of a compound called histamine from the mast cells. The histamine
in turn causes the tissue swelling, difficult breathing, and other
symptoms of anaphylaxis.
Some people have a recurrence of symptoms about six to eight hours
after an episode of anaphylaxis. This recurrence is called a biphasic or
delayed reaction.
Some substances are more likely to trigger anaphylactic reactions
than others. The most common triggers are:
• Foods. Almost any food can cause anaphylaxis in persons who are
sensitive to it; however, peanuts, nuts from trees (walnuts, cashews,
and Brazil nuts), shellfish, fish, milk, and eggs are the most common
offenders.
• Stinging insects. Yellow jackets, honeybees, paper wasps, hornets,
and fire ants are the most likely to cause anaphylactic reactions.
• Medications. The drugs most likely to cause problems include
penicillin and other antibiotics; antiseizure medicines; fluids given
after surgery; antibodies made from horse serum; blood and blood
products; radiocontrast dyes used in certain types of imaging studies;
and morphine or similar pain medications.
• Latex. Latex is a natural material made from the rubber tree that is
often used to make surgical gloves and other medical products.
The greatest danger of anaphylaxis caused by latex occurs when the
rubber material touches moist areas of the body or internal surfaces
during surgery, because the allergen in latex can be absorbed by the
body much more quickly.
• Exercise. Some people develop anaphylaxis when they exercise within a few hours
of eating certain foods.
• Other causes. Although such cases are rare, semen, hormones, and extreme temperatures
have been reported to trigger anaphylaxis in some people.