Early Food Allergen Exposure May Be Protective Against Food Allergies: An Extension Of The Hygiene Hypothesis

Background and Objective: Food allergy affects 6% of U.S. children and 4% of the overall U.S. population. Health officials have recommended food allergen avoidance to prevent food allergies, but according to the Hygiene Hypothesis, exposure to allergens and pathogens is necessary for an effective immune system. The purpose of this study was to challenge conventions and determine whether early exposure might be beneficial rather than detrimental. Participants: 258 teenagers between the ages of 14-18 from a regional high school in New England were studied. Of the 258 participants, 67 had allergies (cases) while 191 did not (controls). Methods: A Food Allergy & Diet History questionnaire was administered to the participants’ parents. 2x2 contingency tables were constructed based on case and control exposure before and after a particular age cutoff for each of 6 common food allergens. Odds of exposure for the cases and controls were calculated and compared in an odds ratio (OR). Significance was evaluated with a P-value in a Chi-square test. Results: The types of food allergies within the 67 cases consisted of nuts (39%), dairy (25%), shellfish (19%), wheat/gluten (9%), eggs (6%), seeds (3%), and other (24%). Exposure to eggs (OR, 0.15 [95% CI, 0.08-0.27]), dairy (OR, 0.32 [95% CI, 0.18-0.57]), and wheat/gluten (OR, 0.18 [95% CI, 0.10-0.33]) before the age of 12 months was most protective against food allergies. Exposure to seeds (OR, 0.19 [95% CI, 0.10-0.36]) and peanuts/tree nuts (OR, 0.19 [95% CI, 0.10-0.36]) before 24 months was most protective, and exposure to shellfish (OR, 0.15 [95% CI, 0.08-0.30]) before 36 months was most protective. Conclusions: Exposure to dairy, eggs, and wheat/gluten before 12 months, peanuts/tree nuts and seeds before 24 months, and shellfish before 36 months of age may be protective factors against food allergies. The results from this study, which demonstrate that early exposure is indeed beneficial, are crucial to rewriting and improving the recommendations of health officials for future prevention of food allergies in children and young adults.