Preventing Food Allergies: What Have We Learned and What More Do We Need to Know?

In recent years, there has been a noticeable surge in the prevalence of food allergies, highlighting a growing concern among individuals and healthcare professionals. This phenomenon has been observed across different age groups and geographic regions, making it a significant public health issue. While the exact reasons for the increasing rates of food allergies remain a subject of ongoing research, several factors have been proposed.

One possible explanation is the hygiene hypothesis, which suggests that reduced exposure to microbes and pathogens in early childhood may weaken the immune system, leading to an increased risk of developing allergies. Environmental factors, such as pollution and air quality, are also being investigated as potential contributors. Further, delaying the introduction of common food allergens has been linked to an increased risk of developing food allergies. It was once believed that postponing the introduction of allergenic foods could prevent allergic reactions. However, recent studies suggest that early and regular exposure to potential allergens, such as peanuts, eggs, and milk (often called early allergen introduction), reduces the risk of developing allergies. 

A meta-analysis published in JAMA reviewed data from 23 randomized clinical trials of early allergen introduction involving over 16,000 infants. The researchers found that introducing allergenic foods earlier (between 4-11 months old) reduced the risk of developing food allergies later in life. Specifically, introducing eggs between 4-6 months old and peanuts between 4-11 months old was associated with a lower risk of developing an egg or peanut allergy.

The study found that evidence for early introduction is strongest for peanuts and eggs, which have had the largest, best-controlled clinical trials. The data for these foods are easy to interpret and let scientists draw strong conclusions. Studies on milk included more variables, such as the timing of introduction, what food was used to introduce milk, and how the study was conducted and data was analyzed, making the data harder to interpret. Still, the trials included in this study make it clear that milk introduction (using yogurt, milk formula, or small amounts of milk powder) is safe for babies. Interestingly, two studies were published after this meta-analysis was completed and were not included. The SPADE and COMEET trials were conducted with better controls and more babies and found that milk introduction effectively prevents food allergies.

However, despite the significant progress researchers have made in the last 10 years, many unanswered questions remain about early allergen introduction.

First, the 2023 meta-analysis found that there have not been enough studies on other allergens like wheat, soy, sesame, and tree nuts to make strong conclusions about the efficacy of early introduction to prevent food allergies. The research has demonstrated that it is safe to introduce these allergens to babies. Still, because these allergies are highly persistent, it is critical to understand how to prevent their development.

Second, the 2023 meta-analysis identified that when clinical trials tried to have parents introduce multiple common allergens using whole foods, parents were much more likely to withdraw from the trial or not meet the feeding goals (e.g., they fed eggs once per week instead of multiple times). Importantly, the study found that studies that used food flours had much lower rates of withdrawal – parents were much more likely to be able to consistently feed allergens to their babies this way. More studies are needed on ensuring parents can maintain allergens in their baby’s diet.

Third, there has never been a randomized controlled trial that measures the dose of allergenic protein needed for early allergen introduction to promote tolerance. The EAT study used a data regression model to determine that a minimum of 2 g of peanut protein per week was necessary to prevent the development of allergies. However, the study was not designed to determine sufficient doses. Therefore, many researchers and clinicians remain unsure about the 2 g protein recommendation, even though it has become relatively common.

Fourth, no trials have directly compared various early introduction time points. The COMEET study assessed cow’s milk exposure from birth, while the SPADE trial began cow’s milk introduction at 1 month of age, and the EAT trial introduced milk at 4 months of age. Other similar variations can be found in peanut and egg introduction studies. Infants in the LEAP trial introduced peanuts between 4 and 11 months of age. Analysis of this data found that earlier introduction was associated with a reduced risk of peanut allergy, but the study was not powered to conclude an exact time point. Therefore, there are still questions on exactly when allergens should be introduced to maximize the benefits and whether or not that time point will be the same for all foods.

Fifth, clinical trials use many different form factors of allergenic foods for early introduction. LEAP used Bamba (peanut puffs) to introduce peanuts, while EAT used peanut butter. EAT used hardboiled egg to introduce egg, while PETIT used freeze-dried egg powder. SPADE and COMEET used cow’s milk formula to introduce milk, while EAT used yogurt. It is still unclear if there are ideal form factors that maximize ease of consumption and the potential to induce oral tolerance.

The past 10 years have seen revolutionary advances in our knowledge of preventing food allergies. The next 10 years are likely to prove just as exciting as we continue to examine these important questions.

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These statements have not been evaluated by the Food and Drug Administration and are not intended to diagnose, treat, cure or prevent any disease.