Eating more egg and peanut in pregnancy did not lower infant allergy in a trial

A diet rich in eggs and peanuts during pregnancy and breastfeeding did not reduce the chance that a baby developed egg or peanut allergy, according to the randomised PrEggNut trial published in the New England Journal of Medicine [s1]. Among infants at high familial risk of allergy, the rate at one year was 7.8% when mothers ate the high egg-peanut diet and 8.4% when they ate a standard amount — a difference that was not statistically significant (relative risk 0.93; 95% confidence interval 0.69 to 1.26; P=0.65) [s1].

The result matters because the idea it tested is intuitive and widely discussed: that exposing the developing immune system to food allergens before birth and through breast milk might train it toward tolerance. PrEggNut is the first large randomised trial to put that specific strategy to the test, and it came back negative [s1].

What the trial did

PrEggNut was a multisite, randomised trial run in Australia [s1]. It enrolled pregnant women whose unborn child had at least two biologic family members — a mother, father or sibling — with medically diagnosed allergic disease, the group at highest baseline risk of food allergy [s1]. Participants were assigned in a 1:1 ratio to one of two diets and asked to follow it from before 23 weeks' gestation until four months after birth while breastfeeding [s1].

The high egg-peanut group aimed for at least 6 eggs and 60 peanuts per week; the standard-diet group ate no more than 3 eggs and 30 peanuts per week [s1]. A total of 1,070 participants were assigned to the high egg-peanut diet and 1,067 to the standard diet [s1]. The prespecified primary outcome was IgE-mediated egg or peanut allergy in the infant at one year of age, confirmed rather than assumed — the study protocol specifies that diagnosis rested on formal food-challenge testing, the reference standard, with allergy sensitisation and eczema as key secondary outcomes [s2].

What it found

Egg or peanut allergy occurred in 83 of 1,066 infants (7.8%) in the high egg-peanut group and 89 of 1,064 (8.4%) in the standard-diet group [s1]. The confidence interval around the relative risk ran from 0.69 to 1.26, meaning the data are compatible with anything from a modest reduction to a modest increase in risk — the hallmark of a null result rather than a hidden benefit [s1]. Safety measures were similar in the two groups, so eating more of these foods did not appear to cause harm either [s1].

How to read it

Three points frame the finding. First, this was a well-powered test of a clean question. The trial was designed around a food-challenge-confirmed primary outcome and enrolled more than 2,000 pregnancies, so a real protective effect of the size many had hoped for would likely have shown up [s1][s2]. That it did not is informative, not merely inconclusive.

Second, PrEggNut tested maternal diet, not infant diet. It says nothing about feeding allergenic foods directly to babies, a separate strategy with its own evidence base pointing the other way. The trial's own conclusion is narrow and specific: eating high amounts of egg and peanut during pregnancy and lactation did not lower infant allergy risk compared with eating low amounts [s1]. Readers weighing the different question of when to introduce solids to an infant can see the evidence on early allergen introduction, which is not what this trial studied.

Third, the population was deliberately high-risk — infants with at least two close relatives who have allergic disease [s1]. Whether the same null result would hold in lower-risk families was not tested here, though there is no obvious mechanism by which a diet that fails to help high-risk infants would help lower-risk ones more.

The trial was funded by the Australian National Health and Medical Research Council and other non-commercial sources, not by a food or pharmaceutical company — a point worth noting given how often dietary claims in this area carry a commercial interest [s1].

Why it matters

Food allergy has become more common in many countries, and pregnant women are frequently told, from conflicting directions, either to avoid allergenic foods or to load up on them. PrEggNut removes one plank from the "load up" advice: deliberately eating more egg and peanut while pregnant or breastfeeding does not appear to protect the baby [s1]. It also offers reassurance in the other direction — women who eat these foods normally are not putting their infants at higher risk [s1].

What to watch

The open questions are whether longer follow-up changes the picture — allergy can emerge or resolve after infancy — and whether any prenatal exposure, dose or timing could matter for tolerance. For now, the most reliable prevention evidence continues to concern what and when infants themselves are fed, not what their mothers eat.

This article describes trial results and is not medical advice. Dietary decisions in pregnancy are for individuals and their clinicians.

Sources

• Trial of a Maternal Diet Rich in Eggs and Peanuts to Reduce Infant Allergy — The New England Journal of Medicine, 16 September 2026 (PrEggNut primary results)
• PrEggNut Study: protocol for a randomised controlled trial — BMJ Open, 13 June 2022 (trial design and outcome definitions)