Can polypropylene microplastics from infant feeding products worsen milk allergies?
A mouse study found oral polypropylene microplastics made cow's milk allergy worse by shifting immune cells toward an allergy response. Human risk is still being studied.
What's actually in it
Polypropylene is a common plastic used in food containers and some infant feeding products. Recent evidence shows polypropylene feeding bottles can release nano- and microplastics during formula prep.
Food allergy starts in the immune system. The gut helps teach the body which food proteins are safe. If that process is pushed toward an allergy response, symptoms can get worse.
What the research says
A 2026 mouse study in Journal of Agricultural and Food Chemistry tested oral polypropylene microplastic exposure in a cow's milk allergy model. The exposed mice had worse allergy symptoms, stronger antibody responses, and more gut barrier dysfunction.
The study also found immune changes. Polypropylene microplastics pushed dendritic cells and T cells toward a Th2 allergy pattern and reduced regulatory T-cell responses that help build oral tolerance.
This is mouse evidence, not proof that plastic bottles cause milk allergy in babies. Still, it supports a simple choice: use glass or stainless steel for formula prep and food storage when possible. If plastic is used, avoid hot water contact with the plastic when you can do so safely.