While
many children who experience food allergies develop symptoms early in life,
others develop sensitivities to certain foods as they reach school age or even
later. The onset of a food allergy can be sudden, and symptoms vary. Once an
allergy is identified, avoiding the food becomes critical, although some
children will outgrow their allergies.
A food allergy develops when the body’s immune system reacts with an antigen,
or foreign substance, in a particular food. The body produces a protein that
reacts with the antigen to release histamine, which causes adverse reactions in
the digestive or respiratory systems, or on the skin. An allergic reaction can
be as mild as an upset stomach or rash — or as severe as gastrointestinal pain,
labored breathing and, in some cases, anaphylactic shock or death, explains
Maria Garcia-Lloret, M.D., UCLA pediatric allergist and immunologist at Mattel
Children’s Hospital at UCLA, and co-director of UCLA’s Food Allergy Clinic.
While any food can be the source of an allergic reaction, according to Dr.
Garcia-Lloret, 90 percent of all food allergies are caused by peanuts, eggs,
milk, shellfish, wheat, tree nuts, soy and fish.
Signs and Symptoms
Allergic reactions to food may manifest in children as hives, which is an itchy rash that
appears within minutes of eating a particular food. Lip and facial swelling may
also occur.
Another common condition, especially in infants, is eczema, a chronic skin
rash that can range from hot, dry itchy skin to more severe cases that leave
skin bleeding and raw.
Food allergies may also cause indigestion, diarrhea or vomiting. “In some
children, gastrointestinal problems or a general failure to thrive may be
misdiagnosed as resulting from stress or poor diet,” Dr. Garcia- Lloret notes.
The most severe and potentially fatal allergic reaction — anaphylaxis —
occurs when the body’s immune system reacts to otherwise harmless food proteins,
resulting in constricted breathing, shock or death. For people with severe
allergies, a doctor may recommend carrying epinephrine, a small dose of
adrenaline, at all times.
In most cases, an allergist can diagnose food allergies using simple skin
patch or blood tests. Physicians, along with a nurse and nutritionist, in UCLA’s
Food Allergy Clinic provide testing and long-term monitoring to understand the
condition and to help implement lifelong dietary changes.
Lifelong Monitoring
Many children grow out of their
allergies by grade school, according to Dr. Garcia-Lloret. While the reasons for
this remain unclear, one theory is that the immune system, which may not have
been fully developed at birth, matures as the child grows. “Children who had a
food allergy before 3 years old should retest in grade school,” Dr.
Garcia-Lloret advises. “Some children follow restricted diets when, in fact,
they are no longer allergic and can begin to enjoy foods that were once
off-limits.”
On the other hand, children who never had allergies but begin to experience
recurrent symptoms such as rashes or stomachaches may have developed a reaction
to a certain food. “As children grow older, they are exposed to more and more
antigens,” Dr. Garcia-Lloret explains. “Once in a while, the antigens may
suddenly become confused, react with each other, and make the child react
differently to a particular food.”
At present, the main treatment for food allergy is strict
avoidance of the allergy-causing food to prevent an allergic reaction. Dr.
Garcia-Lloret advises parents and children to ask questions about ingredients
when eating out, and to read food labels carefully. She cautions, “Learn the
‘code’ words for certain ingredients, which may contain harmful derivatives of
the food your child cannot eat.”