Do early-life bifidobacteria reduce allergies?
Certain bifidobacteria found in an infant’s gut, promoted particularly by breastfeeding, could provide long-term protection against allergies by limiting production of the antibodies involved.
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About this article
Allergic diseases (eczema, asthma, food allergies) often appear very early in life and are becoming more common. They therefore raise a crucial question: how do these allergic traits develop? And how can we counter them?
16 % Food allergen sensitization affects up to 16% of all infants in low- and high-income countries. ¹
A question of bifidobacteria
A study 1 published at the beginning of 2026 in the journal Nature Microbiology suggests that part of the story unfolds very early, through bacterial colonization of infants’ guts. In particular, certain bifidobacteria carry a specific gene (ALDH) that allows them to transform aromatic amino acids from breast milk into their respective aromatic lactates.
These lactates have a beneficial effect on the child’s developing immune system. One of them in particular is 4-OH-PLA, an aromatic lactate that appears to reduce the production of antibodies called IgE (immunoglobulin E), involved in the development of allergies. It is also associated with a lower incidence of atopic dermatitis at two years of age.
x14 Vaginal delivery was associated with a 14-fold higher odds of maternal strain colonization than caesarean section. ¹
A very short time window
These processes occur early and pass quickly: the protective effect of ALDH+ bifidobacteria in the gut microbiota is thought to exist for only a very limited period, up to 5 to 6 months of age. During this period, which generally corresponds to breastfeeding, bifidobacteria are most abundant in the digestive system and 4-OH-PLA production is at its peak. The diversification of the diet (introduction of solid foods) then changes everything.
There may thus be a “critical window” in the infant’s immune development during which a gut microbiota rich in ALDH+ bifidobacteria can have a lasting influence on allergy risk later in childhood and adulthood.
Microbiota imbalance at age one predicts allergies at age five
Factors that support this protective mechanism
According to the study, several early factors seem to be linked to a better establishment of these beneficial bacteria and therefore to higher levels of 4-OH-PLA:
- vaginal delivery, which allows the child to acquire part of the mother’s microbiota, including bifidobacteria;
- the presence of older siblings, also sources of joyful (and beneficial!) bacterial exchange;
- and, above all, exclusive breastfeeding during the first two months, which supports the development of natural protection mechanisms against allergies.
These findings show how much the early months matter in shaping the microbiota–immunity pathway, crucial in the first 1,000 days of life.
1. Myers PN, Dehli RK, Mie A et al. Early-life colonization by aromatic-lactate-producing bifidobacteria lowers the risk of allergic sensitization. Nat Microbiol. 2026 Feb;11(2):429-441.
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