Susanne Brix Pedersen, professor at DTU Bioengineering

Susanne Brix Pedersen

The Early-Life Window: Can Food Allergy Be Prevented Before It Begins?

 in early life was the standard advice. However, new research shows this is not always the case.

A growing body of research now suggests that early exposure, rather than avoidance, may reduce the risk of food allergy and promote immune tolerance during a critical developmental period.

The change began with the Learning Early About Peanut Allergy (LEAP) trial, which showed that by 5 years old, 3.2% of the consumption group and 17.2% of the avoidance group had developed a peanut allergy.

 This represented an approximately 80% relative risk reduction in peanut-exposed children.

Follow-up studies demonstrated that this protection persisted even after a period of peanut avoidance, suggesting durable immune tolerance. A study published in October 2025 analyzed data from > 85,000 children across nearly 50 pediatric practices and found a 27% drop in peanut allergies following the 2015 early introduction guidelines (

 <.001) and a 43% drop after the 2017 addendum (

Building on this dietary prevention model, newer research is expanding attention to early-life immune programming. One area of focus is the infant microbiome, which begins forming at birth and may influence downstream immune responses.

Investigators studying cesarean-delivered infants have examined vaginal microbial transfer as a strategy to partially restore maternal microbial exposure.

 In the ACTIVATE trial, vaginal seeding altered early microbiome composition, shifting bacterial profiles toward those seen after vaginal delivery. Infants who received the intervention also showed differences in food sensitization during infancy, suggesting early microbial exposure may influence allergic risk, although long-term outcomes remain under study.

Mechanistic work has linked microbial activity to immune regulation. Certain bifidobacteria produce aromatic lactate metabolites associated with reduced development of food allergen–specific immunoglobulin E, providing a potential biological pathway connecting microbiome composition to tolerance.

Moreover, translational research examining dietary antigens has identified discrete food-derived proteins recognized by intestinal regulatory T cells; these proteins were found in corn, wheat, and soybean.

 These antigen-specific populations emerge around the time of weaning, when infants first encounter solid foods, and early consumption has been associated with tolerance responses.

These data suggest multiple early-life pathways may influence allergy risk. Microbial colonization, bacteria-derived metabolites, and exposure to dietary antigens each appear to contribute to immune training. This suggests that prevention strategies may extend beyond feeding practices alone to broader early immune development.

: Associate professor of Genetics and Genomics and Immunology at the Icahn School of Medicine at Mount Sinai

An allergist/immunologist at St. Paul Allergy & Asthma and associate professor of medicine at the University of Minnesota Medical School

Clemente J. Vaginal Seeding Partially Modifies Infant Microbiome in ACTIVATE, With Jose Clemente, PhD. HCPLive. Published on March 1, 2026. Accessed on April 13, 2026. 

https://www.hcplive.com/view/vaginal-seeding-partially-modifies-infant-microbiome-activate-jose-clemente-phd

Brix-Pedersen S. Early-Life Bifidobacteria Linked to Lower Food Allergy Risk, With Susanne Brix Pedersen. 

Published on February 4, 2026. Accessed on April 13, 2026. 

https://join.hcplive.com/view/early-life-bifidobacteria-linked-lower-food-allergy-risk-susanne-brix-pedersen

Blum, J. Dietary Epitopes Drive Oral Tolerance, With Jamie Blum, PhD. HCPLive. Published on March 26, 2026. Accessed on April 13, 2026. 

https://www.hcplive.com/view/dietary-epitopes-drive-oral-tolerance-jamie-blum-phd

Gabryszewski S, Gupta R, and Hernandez-Trujillo V. Peanut Allergy Rates Plummet 10 Years After AAP Early Introduction Guidelines. 

 Published October 30, 2025. Accessed on April 13, 2026. 

https://www.hcplive.com/view/peanut-allergy-rates-plummet-10-years-aap-early-introduction-guidelines

Videos

Early allergen introduction, microbiome research, and immune programming studies suggest food allergy prevention may begin during infancy.

 The Early-Life Window: Can Food Allergy Be Prevented Before It Begins?

Early-Life Gut Bacteria Linked to Lower Food Allergy Risk, With Susanne Pedersen

Vaginal delivery, exclusive breastfeeding, and early exposure to siblings emerged as the strongest drivers of colonization with allergy-protective gut bacteria in infancy, offering clinicians a concrete context for how early-life exposures may shape long-term immune risk.

“What we see is that it seems to be very important for the early colonization with these aromatic lactate-producing bifidobacterial that that that you deliver naturally so by vaginal birth,” Susanne Brix Pedersen, a professor at Technical University of Denmark (DTU) Bioengineering, told 

“You can, of course, also introduce these bacteria to a cesarean section-born infant by giving a slurry of the fecal matter from the mother. [It] has been done in a few…studies conducted in the US.”

In a recent longitudinal study, investigators showed that infants colonized early with aromatic lactate–producing bifidobacteria were significantly less likely to develop 

food allergen–specific immunoglobulin E (IgE)

 and atopic dermatitis in childhood. The findings extend earlier work linking the infant gut microbiome to immune tolerance and help clarify which perinatal factors most strongly influence the acquisition of these beneficial microbes.

The study followed 147 children born in Sweden between 2003 and 2005, with fecal samples collected at 8 time points from birth through age 5 years, alongside maternal samples, blood draws, and clinical follow-up. Using genetic and metabolomic profiling, investigators identified a subset of bifidobacteria capable of converting aromatic amino acids into aromatic lactates. Infants with high abundance of these bacteria, particularly during the first 6 months of life, had elevated gut levels of aromatic lactates and a reduced risk of food allergen–specific IgE through 5 years old, as well as lower rates of atopic dermatitis at 2 years old.

Among early-life exposures, vaginal delivery had the most pronounced effect. Infants born vaginally were approximately 14 times more likely to be colonized with these bifidobacteria than those born by cesarean section.

Exclusive breastfeeding during the first 2 months of life also strongly promoted colonization, while early formula supplementation was associated with markedly lower bacterial abundance. Having older siblings further increased the likelihood of early colonization, suggesting a role for household microbial exposure.

Mechanistically, the protective association was mediated by 4-hydroxy-phenyllactate (4-OH-PLA), a bacterial metabolite that selectively inhibited IgE—but not IgG—production in ex vivo human immune cell cultures.

“It's quite important that you…don't see an inhibition of the IgG because the IgG is there to protect us against the different infections that we are acquiring during early life,” Pedersen said. “If we see an increase…or a decrease of that…that might have had some implications in terms of infection burden. Having a selective inhibition of the IgE, which is so IGE is connected to allergic diseases, but also, of course, to the ability of handling a parasite infection. In this case, we didn't see a total IGE inhibition, but an anti-allergen specific IGE inhibition.”

The findings point toward multiple potential prevention strategies, including supporting bifidobacterial growth through breastfeeding-associated substrates, targeted probiotic supplementation in infants with low colonization, or direct delivery of aromatic lactates. For clinicians, the results reinforce the importance of early-life counseling while underscoring that microbiome-based interventions are not yet ready for routine practice.

“[The next step] is actually to convene on these intervention studies to make sure that supplementation to, for instance, C-section born infants, would provide them with the right colonizing bifidobacteria in the early life,” Pedersen said.

Myers PN, Dehli RK, Mie A, et al. Early-life colonization by aromatic-lactate-producing bifidobacteria lowers the risk of allergic sensitization. 

Pedersen S. Early-Life Bifidobacteria Linked to Lower Food Allergy Risk, With Susanne Brix Pedersen. Published on February 4, 2026. Accessed on February 5, 2026. 

https://www.hcplive.com/view/early-life-bifidobacteria-linked-lower-food-allergy-risk-susanne-brix-pedersen

Vaginal delivery, exclusive breastfeeding, and early sibling exposure strongly predicted colonization with bifidobacteria that suppress IgE responses in a recent study.


 Inside the Study Linking Infant Gut Bacteria to Lower Allergy Risk

Infants colonized early with specific bifidobacteria that produce aromatic lactate metabolites were significantly less likely to develop 

 and atopic dermatitis in childhood, according to new longitudinal data published in 

The findings add mechanistic clarity to the long-standing hypothesis that the infant gut microbiome helps shape immune tolerance during a narrow developmental window. In a prospective cohort of 147 children followed from birth to age 5, investigators identified a distinct microbiota–metabolite–immune axis associated with reduced food allergen–specific immunoglobulin E (IgE) and lower rates of eczema

The study, led by investigators at the Technical University of Denmark (DTU), tracked infants born between 2003 and 2005 in Sweden, with serial fecal sampling at 8 time points from birth through 5 years of age, alongside maternal samples, blood draws, and clinical data. Using genetic and metabolomic analyses, the team focused on a subset of bifidobacteria capable of converting aromatic amino acids into aromatic lactates. They wanted to see whether specific diseases could be prevented by having a certain microbiota early in life.

Infants with a high abundance of these bacteria, particularly in the first 6 months of life, had elevated gut levels of aromatic lactates and a markedly lower risk of food allergen–specific IgE through age 5. Infants with high levels of bifidobacteria that produced aromatic lactate metabolites had reduced atopic dermatitis at 2 years old. The protective association was mediated by 4-hydroxy-phenyllactate (4-OH-PLA), a bacterial metabolite that selectively inhibited IgE production in ex vivo human immune cell cultures without affecting IgG.

“Even though that we see that [4-hydroxy-phenyllactate] can reduce IGE production…in human immune cell populations, we don't know exactly why,” said investigator Susanne Brix Pedersen, professor at DTU Bioengineering, in an interview with 

. “We know that humans, but not other animals except chimpanzees…have a specific receptor that can bind to these aromatic lactates, but we haven't been able to see that it's mediated via these receptors ye, so it might be other routes for interaction with the immune cells that has just not been discovered yet, but we do see this reduction.”

Early-life exposures strongly influenced whether infants acquired these bacteria. Vaginal delivery, exclusive breastfeeding during the first two months, and exposure to older siblings were all associated with higher colonization, with vaginally delivered infants up to 14 times more likely to acquire the strains from their mothers.

If confirmed, the findings could inform new preventive strategies—ranging from targeted probiotics to metabolite-enriched formulas—aimed at reducing the growing global burden of childhood allergies and asthma. Pedersen emphasized that this current data does not yet establish causality.

“There's no causal link at this moment,” Pederson said. “As I see it, we have this prospective study where we see associations, but we don't have any studies that have been designed to actually look at the causal interaction at this moment, but we are undertaking a bigger study in 1000 Danish infants, where we are trying to…investigate this in detail.”

Longitudinal data identify aromatic lactate–producing bifidobacteria and the metabolite 4-hydroxy-phenyllactate as key factors in early immune tolerance.

Susanne Brix Pedersen

Articles