Should we or should we not avoid certain foods to prevent allergies?

Current rates of food allergies are 3-4% for adults and 5% for children and they have been steadily rising for that past 10-15 years. Common allergens include peanuts, tree nuts, milk, eggs, and shellfish. There is surely a genetic component to food allergies as demonstrated by the fact that children are up to 7 times more likely to have a peanut allergy if their older sibling also has one. However, there is also a large environmental factor contributing to the development of food allergies. Parents often ask how they can prevent or limit the chances that their children will develop food allergies later in life. Although guidelines from 2000 suggested the avoidance of potential allergens until 1-3 years of age, new research has suggested that this type of avoidance may actually increase the likelihood of a child developing allergies later in life. In a review article published in the Canadian Medical Association Journal, researchers have suggested new guidelines based on recent research and a clinical trial.

The change in guidelines suggested in this article follows the findings of a number of papers over the past 10 years:

  • In 2006 a study found an increased risk of wheat allergy in 1600 children when they were exposed to wheat only after 6 months of age and not earlier.
  • In 2008 a questionnaire study determined that schoolchildren in the UK who were introduced to peanuts later had a 10 times higher risk of developing peanut allergy compared to children in Israel where they are introduced to peanuts early in life.
  • In 2010 a study of 2500 infants researchers found that introduction of egg between the ages of 4-6 months was associated with a large reduction in the incidence of egg allergy compared to those children who had egg introduced later in life.
  • In 2010 as well, a study noted that exposure to cow’s milk at two weeks of age protected against a cow’s milk allergy.

These studies, and many others, prompted an investigation into whether early exposure to peanuts could prevent the development of allergy. This clinical trial, called LEAP (Learning Early About Peanut) randomized over 600 infants who were are high risk of developing a peanut allergy into two groups. Those who received regular peanut consumption and those who avoided consumption until the age of 5. Only 3.2% of the infants who ate peanuts regularly developed a peanut allergy compared to 17.2% of the infants in the avoidance group. To further break it down, infants who initially tested negative for peanut allergy (skin prick test) only developed a peanut allergy 1.9% of the time if they regularly ate peanuts compared to 13.7% of the time in infants who avoided peanuts. That is an 86% reduction in risk. Infants who initially tested positive for a peanut allergy only developed a peanut allergy 10.6% of the time if they ate peanuts and 35.3% of the time if they avoided peanuts (70% reduction).

The results of this clinical trial, coupled with the prior studies, lead to the development of a new set of guidelines that states that children between 4-8 months of age that are at high risk for a peanut allergy and have a negative skin prick test should begin to have peanuts introduced into their diet on a regular basis. If the skin prick test is positive, then the parents should consult an allergist on the possibility of introducing peanuts into their diet. In addition, there is NO EVIDENCE that having mothers avoid peanut or other allergens during pregnancy or nursing affects the development of food allergies in any way.

The original guidelines for peanut avoidance were based on consensus between clinicians and researchers rather than direct evidence from studies and so was prone to errors. These new results suggest that avoidance is incorrect and that under controlled settings, children who are at high risk of developing allergies should become introduced to these foods early. Care needs to be taken however, since anaphylactic reactions are life threatening and any introduction of peanut or other allergen could cause severe problems for children who have an established allergy. As recommended, you should speak with your allergist to book an allergy test and talk about the introduction of the allergen into your infant’s diet.

Image Credit: Allergy food by David Castor 

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One thought on “Should we or should we not avoid certain foods to prevent allergies?

  1. Pingback: Contrary to claims, special infant formula does not protect against the development of eczema or allergic disease | Science Translation

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