Does Early Exposure to Food Allergens Increase Tolerance to Them?
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Food allergies affect 1 percent to 2 percent of American adults, according to the American College of Allergy, Asthma & Immunology (ACAAI), along with about 6 percent of children under the age of 5. While their incidence in the United States has been on the rise for at least a decade, no one knows exactly why food allergies are becoming more and more common. Meanwhile, for those in this group just one crumb of an allergenic food can be deadly.
What is a Food Allergy, and Why do They Occur?
A food allergy occurs because your immune system mistakenly recognizes a certain food as dangerous, and then produces a response against it. Symptoms can range from the more mild skin rash, vomiting and diarrhea to the very serious anaphylaxis, which constricts the airways and requires immediate medical attention.
Though most food allergies begin in childhood, before the age of 2, they can occur at any age and involve just about any food. That said, there are eight foods that cause 90 percent of food allergies, and these are:
While no one knows exactly why food allergies appear in some people and not others, one common factor is heredity. If both of your parents have allergies, you have about a 75 percent chance of being allergic as well, according to ACAAI. Meanwhile, if one parent or one side of your family's relatives has allergies, your risk drops to about 30 percent to 40 percent, while those with no family history of allergies have about a 10 percent to 15 percent risk.
Does Early Exposure to Allergens Help or Hurt Food Allergies?
There is a controversy brewing over the common advice to NOT feed young children highly allergenic foods (like milk, wheat and eggs) until they are anywhere from 6 months to 2 years old. The theory holds that because young children's digestive systems have not yet matured, giving these foods to infants increases the risk that their body will absorb food proteins that may trigger allergies.
However, a new study published in the Journal of Allergy and Clinical Immunology found quite the opposite of this theory. According to the study, which examined premature and low birth weight babies (which have immature gastrointestinal tracts), exposing such infants to food allergens early in life may actually boost tolerance later in life.
Specifically, the researchers found no association at all between age, birth weight and the development of food allergies.
"The theory is that at a young age (less than 3 years), an immature and permeable gastrointestinal tract will result in increased antigen uptake. Thus, highly allergenic foods may be absorbed more easily, increasing the risk for sensitization," said the study's lead author Joel Liem from the University of Manitoba. He continued:
"However, our large, population-based epidemiologic study does not support [this]. A possible mechanism preventing sensitization might be the development of immunologic tolerance to orally ingested allergens in premature infants.
"Such tolerance might result from interaction of high antigen concentration with the immature immune system of the preterm infant ... These data prompt us to ask whether it may be possible that introducing highly allergenic proteins (such as peanut) early in life would tolerize (as opposed to sensitize) a child to that particular antigen."
The researchers are calling for more studies to confirm what is the best way to introduce foods to infants.
Interestingly, their findings are similar to those of the "hygiene hypothesis," which says that children who are not exposed to some dirt and germs at an early age (due to living in an overly sterile, "hygienic" environment) are at an increased risk of allergies. Why? Because their developing immune systems didn't get exposed to many germs, they didn't get a chance to develop a tolerance to them.
What to do if You Already Have a Food Allergy
While researchers uncover more about food allergy triggers, there are a number of resources for those who already have them. These include:
Diligently reading food labels (hidden ingredients, particularly with wheat and peanuts, can be anywhere, but the Food and Drug Administration requires that at least the top eight allergens must be clearly stated on food labels).
Journal of Allergy and Clinical Immunology, Volume 119, Issue 5, Pages 1203-1209
American College of Allergy, Asthma & Immunology