McMaster Studies Identify Early-Life Factors for Food Allergy Development and Gut Bacteria's Role in Peanut Allergy Severity

McMaster Studies Uncover New Avenues in Food Allergy Understanding

Two recent studies led by McMaster University researchers have significantly advanced the understanding of food allergies. These groundbreaking investigations have identified key early-life factors contributing to allergy development and elucidated how the gut microbiome can influence the severity of peanut allergy reactions.

These findings, published in JAMA Pediatrics and Cell Host & Microbe, collectively suggest new avenues for prevention, risk assessment, and therapeutic strategies.

Early-Life Factors in Childhood Food Allergy Development

A systematic review and meta-analysis led by McMaster University, published in JAMA Pediatrics on February 9, 2026, meticulously examined early-life factors influencing the development of food allergies in children.

The study was a monumental effort, involving 2.8 million children globally and synthesizing data from 190 studies. Researchers analyzed over 340 potential influencing factors, utilizing a comprehensive approach that included studies where allergies were confirmed through gold-standard food challenge testing.

"Food allergies are a result of combined genetic, environmental, microbial, and social factors rather than a single cause."

Approximately five percent of children are reported to develop a food allergy by age six.

• Eczema and Other Allergies: Infants experiencing eczema in their first year showed a three to four times higher likelihood of developing a food allergy. Wheezing or nasal allergies also significantly elevated this risk.
• Family History: Children with allergic parents or siblings were more likely to develop a food allergy, with the risk elevating if both parents had allergies.
• Delayed Allergenic Food Introduction: Introducing common allergenic foods such as peanuts, nuts, and eggs later in infancy was associated with increased allergy risk. Babies introduced to peanuts after 12 months were more than twice as likely to develop a peanut allergy.
• Antibiotic Use: The use of antibiotics during the first month of life was linked to a higher risk of food allergy. Use later in infancy or during pregnancy was also associated with an increased risk, though to a lesser extent.

The study also identified several factors not linked to a higher risk of food allergies, providing crucial clarifications:

• Low birthweight
• Post-term birth
• Partial breastfeeding
• Maternal diet
• Maternal stress during pregnancy

The findings aim to assist in identifying infants at higher risk who could benefit from early prevention strategies. Senior author Derek Chu highlighted the need for future studies to incorporate diverse populations, utilize food challenge testing more frequently, and adjust for key factors. The research also underscored a need for new randomized clinical trials and updated guidelines to translate these findings into practical action.

Gut Microbiome and Peanut Allergy Severity

A separate, equally significant study, also led by McMaster University researchers and published in Cell Host & Microbe on March 3, 2026, investigated how bacteria in the mouth and gut may influence the severity of peanut allergy reactions. This research aimed to understand why individuals with similar levels of peanut-specific antibodies can experience varied allergic responses.

The research team analyzed saliva and upper gut samples from healthy volunteers, identifying several bacterial species capable of breaking down major peanut allergens, specifically Ara h 1 and Ara h 2. Rothia species were particularly noted for their ability to reduce the capacity of peanut proteins to bind with antibodies, which is the mechanism that initiates allergic reactions. Staphylococcus species were also identified in laboratory experiments as capable of this degradation.

• Among participants with peanut allergies, those with a higher presence of allergen-degrading bacteria demonstrated a capacity to tolerate greater quantities of peanuts before experiencing a reaction.
• These findings were supported by an independent dataset of 120 children, where Rothia species were found in higher abundance in children with elevated peanut reaction thresholds.
• Pre-clinical experiments, including mouse models, showed that Rothia reduced the amount of peanut allergens reaching the bloodstream, lowered the activation of immune cells associated with anaphylaxis, and resulted in less severe allergic reactions after exposure. This suggested microbial allergen metabolism limited both allergen absorption and subsequent immune activation.

The study suggests a clear connection between the oral and gut microbiome and food allergy severity, implying that microbial composition may help explain variations in IgE-mediated anaphylaxis severity among patients with similar IgE profiles. Peanut allergy is noted as the most common food allergy among Canadian children and a primary cause of allergy-related deaths in this group, with current management focusing on strict avoidance.

The findings present exciting opportunities for novel approaches in allergy prevention and treatment.

These include the potential development of new microbial or probiotic therapies, microbial enzyme supplementation, and the enhancement of oral immunotherapy strategies. Further clinical trials are indicated to assess the effectiveness of modifying allergen-degrading bacterial populations in reducing the risk or severity of IgE-mediated anaphylaxis in clinical practice.

This multicentre study involved collaboration with partners in Spain and the United States.