Food allergy is an important public health concern, due to significant quality-of-life, as well as economic elements. Its incidence is known to vary between populations, while early introduction of allergenic food products has become a recommendation in clinical practice guidelines, in efforts for primary prevention.

According to a systematic review and meta-analysis of 23 randomized trials published on March 27th 2023, in JAMA Pediatrics, earlier introduction of different allergenic food products, within the first year of a child’s life, may lead to less risk of food allergy development, but also a high withdrawal rate from interventions.

The investigators searched for articles related to infants, and randomised controlled trials evaluating the impacts of common allergenic food introductions on the development of immunoglobulin E (IgE)-mediated allergies to food between 1 – 5 years of age, and withdrawal from the food interventions, as a marker of safety and acceptability of trials. Following a screening of 9,283 titles, 23 trials were deemed by the team to be eligible, with a total of 56 articles, and 13,794 randomized participants from which data was drawn. Over 90% of studies took place in high-income countries.

Moderate-certainty evidence from four trials (n=3,295) showed that the introduction of multiple allergenic foods — including cow’s milk, eggs, and peanuts, among others — at ages 2 to 12 months was associated with reduced risk of food allergy, at 1 to 3 years (risk ratio [RR] 0.49, 95% CI 0.33-0.74, I2=49%). Of note, there was also moderate-certainty evidence from five trials (n=4,703), showing that introduction of multiple allergenic foods, at ages 2 to 12 months, was associated with increased withdrawal from the intervention (RR 2.29, 95% CI 1.45-3.63, I2=89%).

Moreover, nine of the analysed trials (n=4,811) showed high-certainty evidence that the introduction of eggs at 3 to 6 months of age was associated with a reduced risk for egg allergy (RR 0.60, 95% CI 0.46-0.77, I2=0%), and high-certainty evidence from four trials (n=3,796) showing that the introduction of peanut at ages 3 to 10 months was associated with a reduced risk of peanut allergy (RR 0.31, 95% CI 0.19-0.51, I2=21%). The evidence for the cow’s milk introduction timing and the risk of allergy to the milk was of low certainty.

Partially, this work is an update of the evidence syntheses for the UK Food Standards Agency in 2016, which has influenced infant feeding guidance in the UK and internationally with key findings, showing that early introduction of egg and peanut reduce risk of allergy to these foods (JAMA).

One of the authors of these studies, Associated Professor of Epidemiology at UNIC Medical School, Despo Ierodiakonou, said:

‘One key aspect of this meta-analysis was the focus on reducing multiple food allergies, rather than just 1 or 2 specific food allergies. The findings support the concept of using earlier allergenic food introduction to prevent food allergy but highlight the need for more acceptable forms of multiple allergenic foods. Notably, most complementary feeding interventions were initiated before 6 months of age, which is against World Health Organization infant feeding guidance and more attention needs to be given on that respect’.