In sports and other competitive pursuits the saying “whatever does not kill you makes you stronger” seems appropriate and possible even comforting. To have this applied to the topic of food allergy, particularly in children, seems anything but comforting. Recent research aimed at understanding the complex problem of food allergy suggests that this principle may not be too far from the truth and underlies a significant paradigm shift in how we approach food allergy prevention. The result is creating a squeeze felt by families with food allergies as well as the physicians who care for them.
Until recently, the American Academy of Pediatrics recommended that infants who were considered at increased risk of developing food allergy because of their family history should avoid peanuts during the first three years of life, milk for the first year, egg until age two, and tree nuts and fish until three years of age. Also, it was suggested that mothers avoid peanuts and other allergenic foods during pregnancy and breast-feeding.
Recently, however, these recommendations were withdrawn by the American Academy of Pediatrics because of a lack of current evidence supporting the assumption that delaying introduction of allergenic food helps to reduce the occurrence of food allergy and other allergic disease. Also noted was a lack of evidence supporting dietary restrictions during pregnancy and breast feeding. Even the World Health Organization’s strategy to prevent allergy by recommending exclusive beast-feeding for the first six months of an infants life has come into question. Although breast feeding until four months of age is still recommended, evidence seems to suggest that prolonging breast feeding beyond 4 months of age may acutely increase the likelihood that a child will develop allergies!
So what options are available to parents and physicians to determine if a child is at risk of a serious food allergy because of a family history or other concerns and how can we prevent or reduce the likelihood of a serious food allergy from developing?
The “dual-allergen exposure hypothesis” is a new theory that may shed light on these questions . This theory suggests that infants come into contact with small amounts of food through the skin as they explore the environment and as a result of this cutaneous contact, become sensitized. Sensitization is the process of developing allergic antibodies to something in the environment. These allergy causing antibodies can be detected on an allergy skin test or blood test.
Sensitization does not always lead to clinical allergy. Why not? Because between sensitization and allergy symptoms is a third factor: tolerance. Tolerance is our bodies way of reining in the inappropriate allergic response, preventing inflammation that we experience as symptoms. We want tolerance: it’s natural and very effective, and without it, we would be at risk of reacting to many of the foods that we require for adequate nutrition.
The second part of the dual-allergen exposure hypothesis states that, although sensitization may occur through the skin, tolerance occurs through oral exposure. In other words, eating the food helps to prevent allergies from developing. The timing and balance of cutaneous and oral exposure determines whether a child at risk will develop adequate tolerance or else develop harmful adverse reactions because of allergy.
The dual-allergen exposure hypothesis has important implications for the use of allergy blood tests in children. The use of blood tests to diagnose food allergy in children may in fact be causing more severe allergy problems because parents are frequently told to restrict from the diet foods that show up on a blood test (indicting sensitization but not necessarily allergy) and in the process, push the child from sensitization to true food allergy.
There is always some risk when a child is exposed to a food for the first time (as there is with taking their first step or attending their first day of school), but in spite of the risk of a few bumps along the way, early oral exposure to a food may in the end make the child stronger and less vulnerable to more serious food allergies in the future.