Nutrition Science and Everyday Application - beta v 0.1

FOOD INTOLERANCES, ALLERGIES, AND CELIAC DISEASE 163
Figure 3.18. The prevalence of lactose intolerance worldwide.
FOOD ALLERGIES
In addition to its role in digestion, the GI tract serves an important immune function.
Intestinal cells form the barrier between the interior of the body and the lumen, or tube, of
the GI tract, which is technically outside of the body and teeming with potential pathogens.
Immune tissue in the GI tract and other parts of the body produce immune cells that target
foreign invaders, in part through the production of antibodies, protective proteins that bind
to foreign substances. However, this function requires the immune system to accurately
distinguish between normal food proteins and invading pathogens. A food allergy is what
happens if the immune system mistakenly identifies a food protein as an invasive threat.
The most common type of food allergy involves immunoglobulin E (IgE), a type of
antibody produced by the immune system in response to a specific substance, orallergen.
Symptoms of an allergic reaction usually occur immediately after consuming the food (i.e.,
within seconds to minutes), although reactions can sometimes be delayed by two hours
or more. Because an allergic reaction is caused by the immune system, it can lead to
symptoms all over the body, including skin rashes; swollen lips, face, or throat; wheezing and
difficulty breathing; nausea and vomiting; cramping; diarrhea; and rarely, a dangerous drop
in blood pressure. A severe allergic reaction involving more than one organ system—a rash
coupled with difficulty breathing, for example—is called anaphylaxis. Anaphylaxis can be lifethreatening
and should be treated immediately with epinephrine, commonly administered