First-Week Immune Reaction Triples Baby Allergy Risk — SkimNews
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- Petter Brodin of Imperial College London presented findings from a study of nearly 600 Swedish infants showing that babies with a strong 'seeding' immune reaction in the first week of life had a 39% rate of eczema or food allergies by age 1, versus 12% for those with a weak reaction.
- About half the infants showed a strong seeding reaction marked by high levels of inflammatory molecules such as interferon gamma, and these babies carried substantially more Bacteroides gut bacteria than those with weak reactions.
- Brodin attributes the brief window to the fact that newborns have a 'leaky gut' that closes after roughly a week, allowing bacteria to enter the bloodstream and activate immune cells.
- Among breastfed babies with strong seeding reactions, only 25% developed eczema or allergies when they had high bifidobacteria levels, compared with 50% when bifidobacteria were low; formula-fed babies with strong reactions fell in between at 33%.
- Bifidobacteria appear to break down sugars in breast milk called human milk oligosaccharides into anti-inflammatory short-chain fatty acids, which may prevent the immune system from overreacting, according to Brodin.
- Lucy Crouch of the University of Birmingham called the work 'a really important piece of work' and said it could inform personalised medicine, such as probiotics for high-risk infants, but stressed further research is needed to establish causation beyond associations.
- Lindsay Hall, also at Birmingham, cautioned that the striking differences in allergy and eczema risk show correlations rather than direct cause-and-effect, and said it is 'much too early' to advise parents to change how they feed or interact with their infants.
- Brodin challenged the prevailing view among immunologists that immune development begins at birth and progresses continuously, arguing instead that the first week constitutes a distinct, disproportionately influential phase.
Why it matters: If the seeding reaction is confirmed as causal, clinicians could one day screen newborns for immune markers and gut bacteria composition, then use targeted probiotics to reduce the roughly 39% allergy/eczema rate in high-risk infants. For now, the finding reframes the first week of life as a critical, narrow window of immune programming, with breastfeeding and bifidobacteria levels emerging as potentially modifiable protective factors.
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