For decades, expectant mothers have faced a quiet anxiety: could something on their dinner plate determine whether their child develops food allergies or eczema?

Peanuts or no peanuts? Dairy or dairy free? Fish oil supplements? Probiotics?

A 2026 scientific review suggests the answer is less dramatic, and more reassuring, than many feared. After examining the latest global research, scientists conclude that there is no consistent evidence that specific foods or supplements during pregnancy or breastfeeding reliably prevent food allergies or eczema in children. The immune system, it turns out, is not so easily programmed by a single dietary choice.

The Rise of Allergies, and the Search for Prevention

Food allergies and atopic dermatitis (eczema) have increased sharply in industrialized nations over the past few decades. Eczema often appears first, sometimes in infancy, and can be followed by food allergies, asthma, and hay fever, a progression doctors call the “atopic march.” Because pregnancy is a critical window of immune development, researchers have long wondered whether a mother’s diet could shape how her baby’s immune system learns to tolerate, or react to, foods.

Biologically, the idea makes sense. Nutrients, immune molecules, and even tiny fragments of food proteins cross the placenta and later pass through breast milk. In theory, these exposures could influence whether a child’s immune system interprets peanut proteins, for example, as harmless or threatening.

But biology is rarely so straightforward.

The End of Allergen Avoidance

In the 1990s and early 2000s, pregnant women were sometimes advised to avoid peanuts, eggs, or milk—especially if allergies ran in the family.

That advice has largely been reversed.

The new review confirms that avoiding allergenic foods during pregnancy or breastfeeding does not prevent allergies in children. In fact, some studies suggest the opposite: higher maternal peanut consumption during pregnancy has been associated with lower peanut allergy risk in offspring. Restricting foods, researchers now warn, may deprive the developing immune system of opportunities to learn tolerance.

The Mediterranean Diet: Healthy, but Not a Cure

What about broader eating patterns? The Mediterranean diet, rich in fruits, vegetables, olive oil, nuts, and fish, has been praised for heart health and longevity. Could it also protect against allergies?

The evidence is mixed. Some studies suggest that strong adherence to a Mediterranean-style diet during pregnancy may modestly reduce the risk of eczema. But the same pattern does not consistently reduce food allergy risk, and several large studies find no clear effect at all.

The Mediterranean diet remains a wise choice for general health, but it is not a proven allergy shield.

Supplements: Hope Meets Uncertainty

Omega-3 fatty acids, often found in fish oil, have attracted particular interest because of their anti-inflammatory properties. Some clinical trials suggest that omega-3 supplementation during pregnancy may lower food allergy risk in early childhood. Yet the protective signal appears to fade as children grow older, and other large studies show no consistent benefit.

Vitamin D and zinc, both important for immune regulation, also fail to show reliable protective effects in current data. Probiotics offer an intriguing twist. Most studies find that when only the mother takes probiotics during pregnancy, there is little impact. But when both mother and infant receive probiotics, some analyses suggest modest protection. Scientists suspect that directly shaping the infant’s gut microbiome may be more influential than maternal supplementation alone.

Still, the evidence is not strong enough to recommend probiotics routinely for allergy prevention.

A New Concern: Processed Foods

While many proposed protective strategies fall short, newer research raises questions about modern diets. Higher consumption of ultra-processed foods during pregnancy has been linked to increased eczema risk in infants. Diets high in certain omega-6 fatty acids, common in industrial seed oils, may also correlate with persistent allergies in some studies. Even high intake of fortified white bread has drawn scrutiny in preliminary research.

These findings remain early and require replication. But they hint that overall diet quality, and not just single nutrients, may matter.

Why Is It So Hard to Find Clear Answers?

Studying diet is notoriously difficult. Unlike a pharmaceutical trial, food research must account for thousands of interacting variables: cooking methods, food sourcing, contaminants, genetics, environmental exposures, and cultural patterns. Many studies rely on food questionnaires and parental reports of allergy, which can introduce error. Randomized trials, considered the gold standard, are harder to conduct during pregnancy for ethical and practical reasons.

As the review’s authors note, inconsistencies across studies reflect these methodological challenges as much as biological uncertainty

What Parents Should Know

For now, the science supports a relatively simple message:

• Do not avoid allergenic foods during pregnancy or breastfeeding solely to prevent allergies.
• Eat a varied, balanced diet for overall health.
• There is no strong evidence that extra supplements, beyond standard prenatal care, prevent food allergies or eczema.
• After birth, introducing a diversity of foods during infancy appears more important for allergy prevention than maternal diet alone.

Allergy development is shaped by genetics, microbiome development, skin barrier function, environmental exposures, and timing of food introduction. Maternal diet likely plays a role, but not a decisive one.​

The Bigger Picture

The hope that a single dietary adjustment during pregnancy could prevent childhood allergies is understandably appealing. But immune development is not governed by simple switches. It is a dynamic, evolving system influenced by many small forces acting together.

In the meantime, the best advice for expectant mothers may be the least dramatic: eat well, eat broadly, and avoid unnecessary restrictions. Science continues to search for clearer prevention strategies. For now, balance, not fear, remains the most evidence based approach.

Reference

1. Morio K, Litonjua A, Venter C, Bunyavanich S, The Role of Maternal Diet andSupplements during Pregnancy and Lactation in the Prevention and Development of Food Allergiesand Atopic Dermatitis, The Journal of Allergy and Clinical Immunology: In Practice (2026), doi: www.doi.org/10.1016/j.jaip.2026.02.028.

2. Amati F, Hassounah S, Swaka A. The Impact of Mediterranean Dietary Patterns During Pregnancy on Maternal and Offspring Health. Nutrients. 2019;11(5):1098. Published 2019 May 17. doi:10.3390/nu11051098

3. Huynh LBP, Nguyen NN, Fan HY, Huang SY, Huang CH, Chen YC. Maternal Omega-3 Supplementation During Pregnancy, but Not Childhood Supplementation, Reduces the Risk of Food Allergy Diseases in Offspring. J Allergy Clin Immunol Pract. 2023;11(9):2862-2871.e8. doi:10.1016/j.jaip.2023.06.005

4. Jiang L, Zhang L, Xia J, et al. Probiotics supplementation during pregnancy or infancy on multiple food allergies and gut microbiota: a systematic review and meta-analysis. Nutr Rev. 2025;83(2):e25-e41. doi:10.1093/nutrit/nuae024

5. Nakano T, et al. Maternal Mediterranean diet adherence during pregnancy and allergic outcomes in offspring: Japan Environment and Children’s Study. Allergy. 2023.