Since the late 1980s, the “hygiene hypothesis” has been an influential cornerstone in the theorized process behind the increasing numbers of children in industrialized countries who are likely to get eczema. There have been two primary approaches to this hypothesis.
This second approach focuses on children who have a decreased exposure to farm animals, who are not born vaginally, and who have limited exposure to siblings or other children at a young age.
Several population based studies have shown that children raised in farming environments are at a decreased risk for developing childhood allergies. Vaginal birth, as well as exposure to siblings, has been shown to strongly impact the infant microbiome, which subsequently affects the child’s risk of developing eczema. Additionally, studies have shown an association between an increased risk of atopic dermatitis and increased colonization by Clostridium.