Early approaches for prevention of food allergy, espoused by the AAP in 2000, focused on having infants avoid allergenic foods.48 These approaches included recommendations to delay the introduction of cow's milk until 1 year, eggs until 2 years, and peanuts, nuts, and fish until 3 years of age. It also recommended using hypoallergenic formula until 6 months of age if human milk was not available. This approach was based partly on studies demonstrating that infants ingesting hypoallergenic forms of cow milk formula and delaying introduction of allergens had less atopic dermatitis than those following unrestricted diets.49 However, epidemiologic and observational studies published after 2000 suggested that delayed ingestion was not protective and may allow more time for sensitization by routes such as skin or respiratory exposure, while mechanisms of oral tolerance are circumvented by a lack of ingestion.50,51,52 In 2008, an AAP clinical report rescinded earlier advice about delaying introduction of allergenic foods and summarized data on atopy prevention through diet.53
Subsequent to the 2008 report, specifically regarding the timing of introduction of allergenic foods, the Learning Early About Peanut (LEAP) study directly addressed the possibility that early peanut ingestion might reduce the risk of developing peanut allergy.54 LEAP randomly assigned 640 infants between 4 and 11 months of age with severe eczema and/or egg allergy to consume or avoid peanut-containing foods until 60 months of age. Mean age of randomization was 7.8 (standard deviation, 1.7) months, but only 18% (n=116 infants) of the total cohort were younger than 6 months at the time of first peanut introduction. At the time of the random assignment, 90% of infants had received formula. The study excluded infants with large (>4 mm) positive skin prick test results to peanut, assuming many were already allergic, and stratified the enrolled infants as having a peanut skin test wheal of 0 mm (not sensitized) or having a wheal that was 1 to 4 mm in diameter. In the intention-to-treat population with negative skin prick test results (n=530), the prevalence of peanut allergy at 60 months of age was 13.7% in the avoidance group versus 1.9% in the early consumption group (P<.001; relative risk reduction, 86.1%), and among those in the skin prick test positive result group (n=98), the prevalence of peanut allergy was 35.3% in the avoidance group and 10.6% in the consumption group (P=.004; relative risk reduction, 70%). Follow-up studies indicated that the approach was long lasting and did not adversely affect breastfeeding or nutrition.55,56,57 On the basis of these results, an expert panel advised peanut introduction as early as 4 to 6 months of age in infants at high risk (with severe eczema or egg allergy, similar to in the study).58 Given that the pathophysiology of protection is likely to be similar for lower-risk infants and on the basis of additional studies in an unselected population,59 the guidelines extrapolated earliest times of peanut introduction based on the degree of risk (see Table 31.4). The preventive effect of early introduction is not lost if the infant is introduced to peanut later than the "earliest" ages described, but the opportunity to add peanut to the diet before sensitization or allergy occurs could decrease as the infant ages without ingesting it. The guidelines describe using infant-safe forms of peanut, providing prescribed amounts to the group at highest risk, and offering allergy evaluations, including serum peanut-specific IgE tests, skin tests, and or oral food challenges, depending on test results and risk assessments.
Table 31.4. Guidelines for Early Introduction of Peanut58
| Infant Clinical Criteria | Recommendations | Earliest Age of Peanut Introduction |
|---|---|---|
| Guideline 1: Severe eczema, egg allergy, or both | Strongly consider evaluation by serum IgE or skin prick testing, and if necessary, an oral food challenge. On the basis of test results, introduce infant-safe peanut-containing foods. | 4-6 mo |
| Guideline 2: Mild to moderate eczema | Introduce infant-safe peanut-foods. | Around 6 mo |
| Guideline 3: No eczema or any food allergy | Introduce infant-safe peanut-containing foods. | Age appropriate and in accordance with family preferences and cultural practices |
See Togias et al58 for full discussion of criteria, screening tests, and modality of introduction of peanut.
As a result of the publication of the LEAP trial54,56 and other additional reports,58,60,61,62,63,64,65,66 the AAP revised its clinical report in 2019 with new recommendations for dietary interventions for the prevention of food allergy.67 Recommendations68 emerging following the AAP guidelines have suggested that there is no protective benefit from the use of hydrolyzed formula. They also recommend that both peanut and egg should be introduced around 6 months after birth, but not before 4 months of age. These recommendations suggest that other allergens also be added to the diet in the same timeframe, and deemphasize allergy testing prior to introduction. There is also evidence to suggest that having a diverse diet is protective of food allergy.
AAP Recommendations for Food Allergy Prevention Through Diet67
There is lack of evidence that maternal dietary allergen restrictions during pregnancy or lactation play a significant role in the prevention of food allergy.
There is no evidence that any duration of breastfeeding prevents or delays food allergy in infants and children.
There is no evidence that delaying the introduction of allergenic foods beyond 4 to 6 months prevents food allergy, including peanut, eggs, and fish.
There is evidence that the early introduction of infant-safe forms of peanut reduces the risk for peanut allergies (see also Table 31.4). Data are less clear for the timing of introduction of egg.