During an allergic reaction, the immune
system responds to a normally harmless
substance as if it were a threat.
In some people, common foods such as
milk,
eggs, and peanuts can trigger such a
reaction. So how does this work?
If you have a food allergy, your immune
system makes a type of antibody
called immunoglobulin E, or IgE.
This class of antibody binds to immune
cells called mast cells and basophils
that circulate throughout your body.
When you are exposed to the food
allergen, it attaches to the IgE antibodies.
This binding signals the immune cells to
release histamine and other chemicals
that cause allergy symptoms, such as swelling 
of the lips, hives, and shortness of breath.
Because mast cells and basophils rapidly release these chemicals,
an allergic reaction typically occurs
within 30 minutes after exposure.
The most severe kind of reaction is called
anaphylaxis,
which can cause a sudden drop in blood
pressure, trouble breathing,
dizziness, and possibly death. People with
food allergy
and poorly controlled asthma are more
susceptible to severe reactions.
An anaphylactic episode must be treated
with a hormone called
epinephrine, which maintains
blood pressure and opens up the airways.
To deal with accidental exposure, people
diagnosed with food allergy
are prescribed a medical device called
an autoinjector
that delivers a single dose of
epinephrine into the thigh muscle.
Antihistamines alone are not an
effective treatment for anaphylaxis.
There is no cure for food allergy.
The best way to manage the condition
is to avoid the allergenic food,
read food labels carefully, wash hands
and household surfaces,
and always carry an epinephrine
autoinjector. If you are accidentally
exposed to a food allergen,
seek medical help immediately. The
National Institute of Allergy and
Infectious Diseases,
or NIAID, conducts and supports
research to better understand,
prevent, and treat food allergy. In 2010,
an expert panel sponsored by NIAID
issued guidelines to assist healthcare
professionals in diagnosing and 
managing the disease.
These guidelines and a summary for
patients, families, and caregivers can be
found on the NIAID website.
