Triggering allergies through exposure

A genetic predisposition to a food allergy is like a genetic predisposition to bruising. Even if you bruise easily, you won’t get a bruise unless you get whacked with something. With food allergy, you’re highly unlikely to develop an allergy unless you’re predisposed to react to a particular allergen and then exposed to that allergen. This sensitizes your immune system to the allergen, making you susceptible to future reactions.
The formula that causes the onset of a food allergy is well known:
Genetic Predisposition + Exposure = Sensitization
After your immune system is sensitized to a particular allergen, exposure to that allergen potentially leads to symptoms. The exposure piece of the equation gets pretty complicated. For those who are predisposed to developing a food allergy, the type of exposure may influence the likelihood that the exposure triggers onset, as the following general tendencies reveal:

• Repeated low-dose exposure to an allergen early in life is most likely to sensitize you to a specific allergen. In other words, you’re more likely to develop a food allergy to an allergen that repeatedly enters your system in small amounts, such as in breast feeding, trace amounts in foods, or even incidental contact.
• Large-dose exposures early in life may make you less likely to develop a food allergy. Odd, but true — increased exposure to an allergen may actually make you less sensitive to that food. Hold on. Don’t start feeing your baby peanut-based formula or advising nursing mothers to gobble up more peanuts. At this point, doctors have no reliable way to implement this observation in a preventive treatment plan. Based on the best information currently available, the recommendation is still to avoid peanut and other common allergens early in life.
• Avoidance diets may or may not help ward off the development of a food allergy. Although my colleagues and I recommend that parents limit exposure to common food allergens early in their children’s lives, research results waffle on the conclusion. While some studies show that avoidance diets early in life ward off the onset of food allergies, others have failed to uphold these results. We commonly see children who are born into allergic families where exposure has been virtually or completely eliminated develop the allergy. The mother may never have eaten peanut during pregnancy or breast feeding, all peanut has been banned from the premises, and incidental contact is highly unlikely, but the child still develops a peanut allergy. My belief is that these children are so genetically prone to developing the allergy that even inhaling a few errant molecules of peanut protein in the grocery store or shopping mall may be enough to trigger the sensitization process.