I think there is a gut bacteria that has been shown to protect against food allergies and that is often wiped out by excess antibiotics in infancy. I’ll still take my 21st century lifestyle but forgot 50 years, the numbers of sufferers are up like 50% in less than 20 which is truly incredible.
Add infant formula to that. Beastmilk fed babies have great gut flora; formula fed do not. Thanks to the womyn’s movement, having babies is oh so convenient.