The theory is supported by the more frequent occurrence of allergies in developed countries compared to developing countries, but also by the higher incidence of allergies in cities compared to villages, where individuals can meet with pathogens of farm animals. Children from small families are also more likely to have allergies than children from families with more children, where there is more frequent contact with pathogens from siblings. Another environmental factor that may promote the predisposition to allergies is a reduction in the diversity of the microbiome - this affects the diet of individuals, but also the diet of the mother during pregnancy, method of delivery, breastfeeding, antibiotics, and the presence of domestic or farm animals in the normal life of individuals.
The theory is supported by the higher incidence of allergies in developed countries compared to developing ones, and in cities compared to villages, where individuals can meet with pathogens of farm animals. Children from small families are also more likely to have allergies than children from families with more children, where there is more frequent contact with pathogens from siblings. Another environmental factor that may promote the predisposition to allergies is a reduction in the diversity of the microbiome - this affects the diet of individuals, but also the diet of the mother during pregnancy, method of delivery, breastfeeding, antibiotics, and the presence of domestic or farm animals in the normal life of individuals.